单看这一句,只是一个简单句,如果是从句,必须要有主句.
比如：I don't know whose the watch is.这时,whose the watch is才是从句,I don't know 是主句.注意这时宾语从句要用陈述语序,就是the watch 要放在is之前.
再比如：I don't know who he is.我不知道他是谁.