a. because of (I try to do my homework because of the noise.) While "because of" usually explains a reason, in this context, it implies the noise is preventing her from doing homework, thus explaining her difficulty.

c. Although (Although she is happy.) This implies a contrast - despite something else, she is happy.

c. despite (We are going to have a picnic despite the bad weather.) This shows they'll have the picnic regardless of the weather.

c. Although (Although she is not well, she didn't pass it.) This shows a contrast - even though she was ill, she didn't pass.

b. Despite (Despite having the best qualifications among all the applicants, Justin was not offered the job.) This shows a contrast - regardless of his qualifications, he wasn't hired.

None of the provided options fit grammatically. The sentence needs a preposition like "for" or "on account of". It would be correct to say: "When she was interviewed, she was praised for her work."

b. Though (Though many people said it was hard work.) "Though" introduces a subordinate clause expressing contrast.

This question is incomplete. It needs a main clause to make sense.

a. after (What Megan prepared for the job after it was not praised.) This implies a sequence of events.

a. despite (Bruce was not praised despite it.) This shows a contrast - regardless of something, he wasn't praised. The sentence would be grammatically better as "Bruce was not praised despite his efforts" or similar.

a. because of (Because of the noise, I try to do my homework.) "Because of" is followed by a noun or noun phrase.

c. Although (Although she is happy.) "Although" introduces a dependent clause, which needs a main clause to form a complete sentence. The other options don't fit grammatically.

c. despite (We are going to have a picnic despite the bad weather.) "Despite" is followed by a noun or noun phrase.

c. Although (Although she is not well, she didn't pass it.) "Although" is the correct conjunction to show contrast between two clauses.

b. Despite (Despite having the best qualification among all the applicants, Justin was not offered the job.) "Despite" is followed by a gerund (having).

b. However (When she was interviewed, she was praised, however, it was not praised.) "However" is used to contrast two independent clauses; a semicolon or period is needed before "however."

b. Though (Though many people said it was a hard work.) "Though" can be used similarly to "although."

This sentence is incomplete. We need the rest of the sentence to choose the correct conjunction. It likely requires a contrast, so options like "although," "though," or "while" (meaning "whereas") would be possibilities.

b. However (what Megan prepared for the job, however, it was not praised.) Again, "however" is the correct choice to show contrast between two independent clauses.

a. despite (Bruce was not praised despite it.) "Despite" is followed by a noun or pronoun. "Although" requires a subject and verb (a clause). It would be correct to say "although he did his best" or "although he worked hard."