根系是指 [ ]
A.主根和侧根
B.植物的主根
C.须根
D.一株植物所有根的总和
答案:D
下列各组物质的名称、俗称、化学式同一物质的是( )
A.氢氧化钠,纯碱,Na2CO3
B.消石灰,生石灰,Ca(OH)2
C.氯化钠,食盐,NaCl
D.硫酸铜晶体,胆矾,CuSO4
--Tom,you didn't come to the party last night?
----I _____,but I suddenly remembered I had homework to do.
A,had to B, didn't C,was going to D, wouldn't