I find _______ difficult to remember everything, though I'm still young.
A:that
B:this
C:it
D:its
绿色植物白天进行光合作用;晚上进行呼吸作用.(判断对错)
制药厂常将药物封装在淀粉制成的胶囊中口服,以免对胃产生刺激.从消化特点看( )