题目

Every day, Director of Admissions（招生办）Ingrid Hayes and her fellow workers answer calls from anxious parents wanting to know how their child is doing. “I know they want to give an extra push and we understand that,” Hayes said, “but we really do want the students to take center stage in the process.” These over-involved（过分介入）moms and dads have come to be known as “helicopter parents”. Hayes said they are a bigger part of the college admissions process than ever. Psychologist（心理学家）Mark Crawford explained the term comes from the idea of hovering（盘17．下列关于热机和环境保护的说法中，正确的是（　　）A．所有的热机都用汽油作燃料B．汽车排出的尾气都是有毒气体C．热机的大量使用会造成环境污染D．热机所产生的噪声，可以被热机上的消声器完全消除