A:clean
B:cleaning
C:cleaned
D:to clean
— !
如图是a、b两种物质的质量与体积的关系图象,分别用a、b两种物质制成两个规则的实心长方体甲和乙.下列说法中正确的是(ρ水=1.0×103kg/m3)( )
—I've been working on a research report, which was ________ easy. Which of the following can't be put in the blank?