The first sentence is correct. "We" should be used, as it is a subject pronoun. "Us" is an object pronoun - for example, "She gave the instructions to us."

"To duck into" is an idiom based in the verb "duck," which means to bend down suddenly. "To duck into" a place, therefore, means to quickly go into a certain location. Sample usage: "Let's duck into this store so we can avoid the rain."

To understand this [partial] sentence, let's first parse the sentence and eliminate non-vital phrases: "... urging the special congressional committee formed in the debt-ceiling deal this month to identify even more savings than the $1.5 trillion it has been tasked with finding." The phrase "formed in the debt-ceiling deal this month" modifies the noun "the special congressional committee" and can be removed without changing the sentence's main meaning: "... urging the special congressional committee to identify even more savings than the $1.5 trillion it has been tasked with finding." Next, notice that the use of the "more than" phrase, which means that the sentence is making a comparison. In this case, the noun "savings" is inserted right in the middle of the "more than" phrase. Consider the following example: "This is more food than I can eat." The above sentence can be re-organized as: "This food is more than I can eat." In both cases, there is a comparison between (a) this amount of food available and (b) the amount of food that I can eat. In your example, therefore, the sentence makes a comparison between (a) the amount of savings it has been tasked with finding and (b) the amount of savings that hope to be identified. So, the special congressional committee has been tasked with finding $1.5 trillion in savings, but it is hoped that the committee can find savings beyond its original target.

"Warming" is the process of adding heat to something. For example, "I was warming my hands over the fire." "Warming up" is a term to describe light stretching and exercise (e.g. jogging) to stretch out your muscles before a work-out.

Celia, your written English is actually quite good - you should be proud.  I've made some minor corrections below, mostly with capitalization and preposition usage (of, at, for).  I am not familiar with the TOEFL IBT test, but is there an oral section?  If so, you should consider practicing your spoken English with a native speaker.

Hi!  My name is Celia Liu.  I'm a college student and my major is architecture.  I really like to study English, but I don't know how to improve quickly!  I have to take the TOEFL IBT test on October 31th.  Speaking is a big problem for me, so I write instead.  I don't know how to express my thoughts in english.  So friends, please give me some advice!  By the way, I am so happy to find a place to meet different people from all over the world!  To all my new friends, let us improve together!!

In this case, "basic" is a chemistry term related to the pH scale, which measures the acidity or basicity of an aqueous solution. By definition, the scale runs from 0 to 14. Any solution with a pH between 0 and 7 is considered acidic; between 7 and 14 is considered "basic" (or "alkaline," which is the technical term); a pH of 7 is considered neutral.

Mary's answers above are correct, but let me give some more explanation: 1) The correct verb is "use" and not "uses," in order to maintain parallel sentence structure. This is indirectly related to the use of "would," an auxiliary verb, in the sentence. It would keep ___ and only use the system to ___... In the above example, the auxiliary verb "would" applies equally to both verbs - think about breaking the sentence into two parallel parts: It would keep ___. It would only use the system to ___. [correct] It would keep ___. It would only uses the system to ___. [incorrect, non-parallel sentence structure] However, if the auxiliary verb is not necessary in the sentence (depends on your intended meaning), then consider the following: It keeps ___ and only uses the system to ___... Now, in this example, the two verbs (to keep and to use) need to be parallel with each other and also match with the noun ("it"). Again, think about breaking the sentence into two parallel parts: It keeps ___. It only uses the system to ___. [correct] It keep ___. It only uses the system to ___. [incorrect, wrong verb conjugation in first sentence] It keeps ___. It only use the system to ___. [incorrect, wrong verb conjugation in second sentence] 2) Yes, Mary is correct - the sentence should be "You must leave at the right time."

To add on to the response from fdmaxey, "buck" is an informal (slang) term for a dollar. Based on your profile, I see that you are from China. This distinction might make more sense if you consider the following analogy: Formal name: United States dollar is to Renminbi (人民币), as Common name: Dollar is to yuan (元), as Informal name: "buck" is to kuai (块)