若a=8.7,则-a=____,-(-a)=____,+(-a)=____.
下列诗句中描述气候的是( )
张霞在日记里写道“放学时,铃声是悦耳的;考试时,铃声是紧张的;思考时,铃声是刺耳的,”这说明( )
I thought _______ very useful to know the customs of foreign countries.