They are required ________（process）the food that we eat， to recover from injury and for several other bodily functions.
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答案：to process
巧记：（1）在形容词后用不定式，可将I’m sorry to hear that. 作为公式来记忆。（2）做目的状语用不定式;（3）在受序数词修饰的名词后用不定式;（4）在require sb to do sth等结构中用不定式。