建国以来，我国农村生产关系的变化、调整经历了四个步骤依次应为（    ）

①土地改革       ②农业合作社

③人民公社化     ④家庭联产承包责任制

Dear Jack,

    I am very busy____Friday. At 8:00 I have math. It is not fun. The teacher says it is____ but I think it is difficult.____ that, I have P.E. at 11:00. It is easy____fun. Lunch is____12:00 to 1:00. I have Chinese at 1:20. It is my____subject. My classes____at 2:00, but then I have____art lesson for two____. It is really____.

    How about you?

Yours,

Lucy

日军侵华期间，在占领区设立许多制造毒气的工厂或化学武器装配厂，先后一千余次使用了糜烂性毒剂、刺激性毒剂和窒息性毒剂化学弹，杀害了许许多多中国军民。下列反映这方面历史真相的证据中，最具说服力的是（    ）