句子中once a week前要不要加介词at?

句子中once a week前要不要加介词at? i borrow books once a week.books和once之间要不要弄什么 把下列句子改成特殊疑问句 He plays football once a week.once a week 划线 often和usually能不能与 once a week 用在一个句子中? 意思once a week once a week these are fiowers once watered a week 组成句子 英文中once a week用什么时态啊? once a week和twice a week We should feed them once a week.you them?(you前有3格,them前有一格,对划线部分提问,画线部分为once a week) once a week的英文翻译 more than once a week once ,only,some,a,twice,ewwk,or 把这些单词组成句子是week week.it .twice.some.or.once.only.a.eat.组成句子. He climbs the mountains once a week.(用this time yesteday作时间状语改写句子) we go to the movie once a week 对画线句子提问 句子改错 Some boys play basketball once and twice a week Mary visits her parents ( once a week.) ( )( )( )( )( ) her parents?以上面括号中的句子完成下面