Question

complete the text with the correct pair of words. the biologist the slide under the microscope and _ began analyzing the cellular structure of the muscle tissue. set... then set... than sit... than sit... then

Explanation:

To solve this, we analyze the context and word meanings:

1. For the first blank, "set" (past tense of "set", meaning to place) is correct, while "sit" means to rest, so "set" is appropriate here.
2. For the second blank, "then" (indicating sequence) is correct, while "than" is used for comparisons, so "then" fits the context of the biologist first placing the slide and then analyzing.

Answer:

A. set... then