I was going to answer you, but it looks like you've received some excellent comments already! Best of luck! :)

Shalom, Shay! 1. They noticed that when people fast-forward a DVR, they actually concentrate intensively on the screen. - Are concentrating: "They noticed that when people are fast-forwarding a DVR, they are actually concentrating on the screen". This would be right if the verb "fast-forward" was in the same tense. - Are concentrated: "They noticed that when people fast-forward a DVR, the are concentrated on the screen". This seems as if you're trying to make it look as if people were physically on TV. 2. This means they may be paying more attention than they would if the advertisement were playing normally. - Be payed: "This means they may be payed more attention"... / It's a no go, since it's passive tense, here's the correct use of it: "This means the advertisement may be payed more attention to, if they were playing normally." - Have payed = "This means they might have payed more attention"... / It shows it as something that happened only once in the past and in the sentence, we are talking about something that keeps happening. - Was playing = when talking hypothetically, we use "were". A perfect example is: "I wouldn't go there if I WERE you!" I am not you, but I tell you how things would be if that was the case! Now with your sentence: "... IF the advertisement WERE playing normally". The advertisement is not playing normally at the moment, but they imagine what things would be like if it were. - Had been playing = past tense

I think you may have confused people as to what it is you are asking. Select the correct word for each question numbered 13,16,17 from each of the 3 options provided indicated by a,b or c. Adam Brasel and James Gips of the School of Management at Boston College in Massachusetts. They noticed that when people fast-forward a DVR, they actually concentrate. The answer is a. (13 CONCENTRATE– b are concentrating - c are concentrated) intensively on the screen, looking out for the end of the advertising break so that they can get back to their program. This means they may BE PAYING. The answer is B (16 a be paid – BE PAYING – c have paid) more attention than they would if the advertisement HAD BEEN PLAYING, NORMALLY. The answer is C. (17 a was playing – b were playing – c had been playing) normally. the answers in terms of simple past present and future only are. a= THEY ACTUALLY present, b= may BE PAYING = present. c= had BEEN PLAYING = past.

13 is zero conditional (when it's like that it's always that way) so present indefinite is needed (a) 16 is active infinitive without "to" after a modal verb (b) 17 is a hypothetical action "were" is probably more formal although "was" wouldn't be a mistake as "advertisement" is singular anyway. Those aren't the words that point to the answer but the context.