Tom needs some help ________ his homework. Can you help ________?
青少年遇到非正义的事情,既要勇敢,又要机智。遇到不法分子,下列做法中不可取的是( )
对于集合M,N,定义:M-N={x|x∈M且x∉N},M⊕N=M-N∪N-M,设A={y|y=x2-3x,x∈R},B={x|y=log2(-x)},则A⊕B=( )