A:can't have
B:could not
C:couldn't have
D:shouldn't have
下列数据最符合实际的是( )
已知命题p:∃x∈R,x2+2x+a≤0,若命题p是假命题,则实数a的取值范围是____ .(用区间表示)
下列措施中,不属于预防接种的是()