在植物的茎里，运输水分和无机盐的结构是 _____ ，运输有机物的结构是 ______ 。
导管；筛管
根据《合同法》第十六条规定，要约在( )才算生效。
A．要约人发出要约时
B．受要约人了解要约内容时
C．要约到达受要约人时
D．受要约人接到要约前
.
______ pressure the U.S. government put on the Chinese government, China would stick to its own policy of exchange rate.
A．However
B．Wherever
C．Whoever
D．Whatever
