根据所给汉语提示将下列句子补充完整（每空一词）。
小题1:He often ________ ________ some useful advice. (提出)
小题2:It’s very dangerous to ________ _______ _______ these viruses without any protection. （暴露在…之下）
小题3:He ________ the apples _______ four parts. (分成)
小题4:Plastics have ________ ________ ________ ________many conventional (传统的) materials. (代替)
小题5:It was so dark he ________ ________ ________her at once. (看不见)
