EDIT: whoops, didn't see the other answers. sorry! This is referring to "bitcoin mining", which is the process by which new bitcoins are created. The speaker means that there are only two ways you can get bitcoin: by trading for it, or by "mining" it.

They both sound correct to me. If you use "it", it sounds like you're saying "I love doing extreme sports", if you use "them" it sounds like you're saying "I love extreme sports".

Depends on dialect I guess. In my dialect (Southern English) I would prefer "I plucked up the courage" to "I mustered the courage" or "I gathered the courage". The last one sounds the weirdest to me.

Finally, a week in my new university passed. It's already 7:42 am and I'm ready for today's classes. Actually, I'm sad that I have to study really hard from now on. Last week was an orientation week, so we had no classes and no assignments. From this week, things will be different. I know universities are places where we take classes and do assignments, I just miss the times when I was so bored that I had to look for something to do on my own.

Oh! And my dormitory life! I think I'm quite enjoying it. My roommate is nice and I love my desk, bathroom, etc. And I really love cafeteria food for students in the dormitory. The food is kind of salty, but there aren't any other places where I can have homemade food around here.

I have morning classes at 11 am and I have to get ready for them soon. Three hours are lsdt (?) till then. What should I do? Oh! Maybe I should go to the library <strike>in</strike> on the university campus! I'll have breakfast first! I hope you have a great day!

Obeying rules will constrain children’s <strike>imaginary</strike> imagination, so that they cannot solve questions in different ways. Children dare not <strike>to</strike> <strike>practice</strike> express their own thoughts, because they are afraid of <strike>having punishment</strike> being punished if they do not obey the rules. If students are <strike>requested</strike> asked to use one method to write a passage, they do not know the result when they describe their ideas <strike>in</strike> using other methods. The problems met in work are complex and people without creativity will have no idea <strike>about</strike> how to deal with them.

Dear Mr Williams

I’m writing you this letter to <strike>get information</strike> enquire about the language courses in London at the Big Ben School of English. There are some issues that I would like you to clarify.
First, I would like to know how many students there will be in the school and in each class, because I have Attention Deficit Disorder (ADD) and I need a friendly atmosphere surrounding me <strike>which helps me to flourish my motivation</strike> in order to flourish. Furthermore, I would also like to know what qualifications the teachers have because they will have to be reported on (experienced with?) my situation. Due to the variety of activities the school offers, I would like to ensure <strike>if</strike> the price covers everything, and if the school area has <strike>several</strike> amenities like a bus stop or bike shed. Finally, it would be <strike>incredibly</strike> great to know more about the resources the school has for a student with ADD or similar situations.
I’m looking forward to hearing your response. Feel <strike>utterly</strike> free to write me if you want to ask me anything else.
Yours sincerely,
Brian