"Things really took off when Microsoft Windows was introduced in 1985."- In this sentence "took off" refers to ______.

In the given sentence, "took off" refers to a sudden rise in popularity.

Let's analyze the options:

a) Replacement of older version: This option suggests a replacement of an older version, but "took off" typically implies a sudden increase or success rather than a replacement.

b) Sudden rise in popularity: This option accurately reflects the meaning of "took off." When something "takes off," it experiences a sudden increase in popularity or success.

c) Rise in competition: While the introduction of Microsoft Windows might have influenced competition, "took off" specifically emphasizes the rapid and successful growth rather than competition.

d) Price increase: There is no direct indication in the sentence that "took off" refers to a price increase. It typically implies a surge in popularity or success rather than a change in price.

Therefore, the most appropriate interpretation of "took off" in this context is a sudden rise in popularity.