The pupils in our school like reading after lunch, most of ________ seated on the grass unless it rains.
A:them
B:whom
C:that
D:who
玻璃中加入二氧化钒可以有选择地吸收和反射色光,二氧化钒(VO2)中钒元素的化合价为( )
化简:8=____