Fill in the blank with the most appropriate word:
They ______ to London in 1995.

In the given sentence "They moved to London in 1995," the most appropriate word to fill in the blank is "moved."

The verb "moved" is in the simple past tense, and it is used to describe a completed action that took place in the past. The sentence is referring to an event that occurred in 1995 when the subject "They" relocated to London.

The other options do not use the correct verb form for the given sentence. Option A, "move," is in the base form and does not indicate a specific past action. Option C, "is moving," is in the present continuous tense, which does not match the past timeframe mentioned in the sentence. Option D, "has moved," is in the present perfect tense, which also does not fit the context of referring to a specific past event.

Therefore, the correct answer is "B. moved."