Last summer, I worked a volunteer for a month. It is unforgettable for me.
A:at
B:for
C:with
D:as
已知1cm3的氢气重约为0.00009g,一块橡皮重45g
(1)用科学记数法表示1cm3的氢气质量;
(2)这块橡皮的质量是1cm3的氢气质量的多少倍.