2b) I presume from your answer to 1b that this should be the name of the correct verb form, in which case your answer is not correct- the present continuous is be + present participle- I am reading/she's reading a novel.
This means that c) is wrong as the verb form you have given in 2a) uses the auxiliary verb have + past participle. Also, I think they're probably after the reason the past simple doesn't work here, so look at how the forms I saw/didn't see and I have seen/haven't seen relate to present time.
The others are fine.
Student or Learner