Answer:
<em>1. If you cannot see without your glasses, you should not be driving.
</em>
<em>2. Our flight has been delayed because of the thunderstorm.</em>
<em>
3. Though I don’t doubt his sincerity, I cannot agree with his position on that issue.</em>
Explanation:
A complex sentence contains an independent clause along with one or more dependent clauses. Moreover, these sentences/ clauses are joined or linked by appropriate conjunctions.
As given in the rules in the question, if the independent clause comes before the dependent clause, then the use of a comma is unnecessary whereas it is vice versa for when a dependent clause comes first.
Therefore, the given sentences will be punctuated as follows-
<u><em>1. If you cannot see without your glasses, you should not be driving. </em></u>(Comma is used as the dependent clause comes before the independent clause)
<u><em>2. Our flight has been delayed because of the thunderstorm. </em></u>(The independent clause comes before the dependent clause, so the comma is omitted)
<u><em>3. Though I don’t doubt his sincerity, I cannot agree with his position on that issue.</em></u> (Comma is used as the dependent clause comes before the independent clause)