A:Fe3+、K+、Cl-、NO3-
B:Ag+、Na+、NO3-、Cl-
C:Zn2+、Al3+、SO42-、Cl-
D:Ba2+、NH4+、Cl-、HCO3-
读“长江水系图”填空.
There are fewer and fewer tigers in India. The situation will continue ______ humans stop hunting them for their fur and bones.
如图所示,物体放在水平地面上,在拉力F作用下做匀速直线运动,如果重力突然消失了,以下说法正确的是( )