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... then sit... than

Explanation:

"Set" is the appropriate verb as it means to place the slide under the microscope. "Then" is used to indicate a sequence of events. "Sit" is incorrect for placing the slide, and "than" is a comparative word, not for sequencing.

Answer:

A. set... then