用所给词的适当形式填空①We {#blank#}1{#/blank#} (learn) eight units by the end of last week.
② The camera is used for {#blank#}2{#/blank#} (take) photos.
③Mum added lots of salt on the food but it still wasn't {#blank#}3{#/blank#} (salt) enough.
④The ice will soon change into water if you {#blank#}4{#/blank#} (heat) it.
⑤The pretty girl gave me a {#blank#}5{#/blank#} (please) smile.