某元素R的最高价氧化物化学式为RO2,且R的气态氢化物中氢的质量分数为12.5%,则R元素为 ( )
Please _______ the water when you brush your teeth.( )
turn down
turn off
turn on
turn up
﹣Many boy students think math is ______ English.
﹣I agree.I'm weak in English.( )
much difficult than
so difficult as
less difficult than
more difficult than
Do you want to be healthy?______.Smiling can help you stay healthy.( )
Smile
Smiling
Smiles
Smiled
﹣I want to borrow the book,but I don't know how long it may ______.
﹣For two weeks.( )
keep
be borrowed
borrow
be kept
I hope everyone can care about ______ the environment and stop ______ things.( )
protecting; wasting
protecting; to waste
protect; wasting
protect; to waste