Hangzhou is __________ to hundreds of foreign friends who are working and studying here.
A:home
B:house
C:family
D:room
下列句子中,没有语病的一项是( )
下列说法不正确的是( )
对任意两个非零的平面向量α→和β→,定义α→∘β→=α→·β→β→·β→.若平面向量a→,b→满足|a→|≥|b→|>0,a→与b→的夹角θ∈π4,π2,且a→∘b→和b→∘a→都在集合{n2|n∈Z}中,则b→∘a→=( )