A compound complex sentence has at least Main clause(s) and at least Subordinate clause(s).

A compound-complex sentence is comprised of at least two independent(main) clauses and one or more dependent(subordinate) clauses.

Explanation:

Compound Complex Sentence: a sentence having two or more coordinate independent clauses and one or more dependent clauses

Example: Though Mitchell prefers watching romantic films, he rented the latest spy thriller,   and he enjoyed it very much.

Example: Laura forgot her friend's birthday, so she sent her a card when she finally   remembered.

Because compound-complex sentences are normally longer than other sentences, it is very important to  punctuate them correctly

1. c- the tunnel project was worthwhile.

2. b- to inform about the value of the tunnel project

b is the correct answer