用所给词的适当形式填空

①We ____ (learn) eight units by the end of last week.

② The camera is used for ____ (take) photos.

③Mum added lots of salt on the food but it still wasn't ____ (salt) enough.

④The ice will soon change into water if you ____ (heat) it.

⑤The pretty girl gave me a ____ (please) smile.