题目

Half of the workers here ________ under 30 ________. A.is;years              B.are;year old   C.is;years old            D.are;years of age 答案：D 解析: half作主语时，谓语要与half后面的名词保持一致。workers是复数，谓语也要用复数。方程 +x=15的解是6．