Answer:
A: I was sad when I saw the tent collapse.
Explanation:
A correct sentence contains the full elements of a sentence and expresses a full thought. In other words, a correct sentence makes a complete sentence and does not leave the sentence hanging.
The given sentence "when I saw the tent collapse" is a dependent clause, which means that it does not complete the expression. Thus, it is not a complete sentence and requires an independent clause to be complete.
So, adding "I was sad" will complete the sentence to the dependent clause "when I saw the tent collapse".
Thus, the correct sentence is option A.
