A:used to drink; is used to drinking
B:used to drinking ; drinks
C:is used to drinking; used to drink
D:is used to drink; is drinking
①调查人类遗传病
②探索生长素类似物促进插条生根的最适浓度
③培养液中酵母菌种群的数量的变化
④土壤中小动物类群丰富度的研究