【正确答案】 D

【答案解析】[解析] 划线词词义是“精力旺盛的”。
A项happy幸福的；例句：They had a very happy marriage.他们有个幸福美满的婚姻。
B项alone单独的；例句：I was alone in the classroom.我单独一个人在教室。
C项busy繁忙的；例句：Are you busy today?你今天忙吗?
D项energetic精力旺盛的；例句：His son is an energetic child.他的儿子是个精力旺盛的孩子。
很明显D项正确。