Sentence improvement

Please advise me in these question. I got stuck in these.

1) I was waiting until everybody ____ the meeting place.

a) left
b) had left
c) would have left

Ans:- (b)

Shouldn't the answer be (a)?

2) A basic step for career planning,and also for preparation for interviews is to give serious thought _____ by taking stock of your needs , interests as well as

your strengths and weaknesses.

a) to assess yourself
b) to assessing yourself
c) to having assessed yourself

Ans:- (b).

Why can't we use (a) here?

Please help me out in the above sentences.

3.The situation remained the same, rather got worse, _________________.

a) for all his efforts withstanding
b) with all his efforts withstanding
c) inspite of all his efforts not withstanding
d) all his efforts withstanding

Ans:- b

I have read somewhere that 'Notwithstanding' when used as a preposition means 'despite something' or 'inspite of'
e.g Notwithstanding the bad weather, the ship arrived on time

and 'Notwithstanding' when used as an 'adverb' means 'However'

e.g he doesn't want me there, but I am going, notwithstanding

My question is :- Does 'notwithstanding' in the main sentence used as 'adverb' and means 'however' ?

4. He gave evidence at the sensational trial.

Can anyone tell me what 'sensational trial' here means?

5.He ____ with all kinds of people.

a) makes friendship
b) makes friend
c) made friendship
d) makes friends

Ans:d
Shouldn't the answer be (a)?

6. He was sure that given enough time contentious issues _____ .

a) would be sort themselves out
b) would be sorted out
c) would sort themselves out
d) will sort themselves out

Ans:- c

Shouldn't the answer here be (b)?

7. Even though viable alternatives exist, their use is yet to catch on ______.

a) in a major way
b) under a major way
c) into a major way

ans:- a

That would be grate if anyone can tell me what the above sentence would mean?

8. I ____ in Dehradun for ten years when i was a child.

a) had lived
b) had been living
c) was living
d) lived

ans:- a

I believe the answer should be (d) ?

9.When the clock strikes twelve, I ___ here for four hours.

a) I shall have been waiting
b) I would have been waiting
c) I shall have waited
d) I would have waited

Ans:- c

Shouldn't the answer be (a)?

10. Just ______, he could complete the work to my satisfaction.

a) in a hour's time
b) in an hour's time
c) in the duration of an hour

Ans:- b

Isn't (c) equally correct?

11. His idea of reducing the quality of the article to cope up with the increasing market prices was not ___ .

a) welcomed
b) taken for granted
c) agreed to

Ans:- a

Isn't answer(c) also correct? if not, can anyone tell me the difference ?

Appreciate your help!

Thank you!