Q:若V为一向量空间，W为V的子集且为一向量空间，则W为V的一子空间。
ANS:(X)
No. This should make sure that the field and the operations of V and
W are the same. Otherwise for example, V = R and W = Q respectly.
Then W is a vector space over Q but not a space over R and so not
a subspace of V .
请问W为V的子集
为何W跟V 却可能不是布于同一体??
假设V布于R 子集W不也都布于R吗??