I __________ anything because they were so expensive.
A:didn't buy
B:bought
C:not buy
D:didn't bought
①结束了松散状态,维护了国家统一
②满足了人民群众对权益的要求
③确立了美国的责任内阁制
④促进了美国资本主义的发展
如图是成熟植物细胞结构模式图,请据图回答: