It has been years ________ I returned home.
正确答案： C
本题解析：
译文：我回家已经有好几年了。此题考查连词 since 的用法。 since 表示“从 (过去某事 )以来，以后或到现在”时，主句多用完成时态。又如：Where have you been since I last saw you? 自从我上次见到你以后，你到哪去了 ?
Washing the food down with water as a substitute ________ chewing is not a good habit
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Police are ________ the disappearance of two children.
Each of us should _______ aside a few minutes to have a rest every day.
We were told that the stone figure _______ back to the 16th century was of great value.
Perseverance is a kind of quality and that is _______ it takes to do anything well.
You should help them ________ when your friends quarrel with each other.
We are interested in the weather because it _______ us so directly—what we wear, what we do and even how we feel.
—David has made great progress recently. — _______，and _______.