When the independent clauses of a run-on sentence are closely connected in meaning, the sentence can be corrected by joining the two clauses with a
a. adjective.
b. preposition.
c. comma.
d. semicolon?

d. semicolon

Explanation:

A run-on sentence is a sentence consisting of two or more independent clauses (clauses that express a complete thought) that are not connected by a period, semicolon or a conjunction and that, instead, are connected improperly with a comma or that are not connected with any other punctuation.

When a run-on sentence, then, has two independent clauses that are closely connected in meaning, it can be corrected by joining the two clauses with a semicolon because one of the uses of semicolons is to link two independent clauses whose ideas are closely related and that are not linked with a conjunction like and, but, or, nor, for, yet, or so.

the answer is b. the tomb is underground and dark, and its opening is covered by a heavy grate.

a. to introduce the audience to important characters .

b. to inform the audience where the story takes place .

e. to lay out specific details about different plot points.