要使分式有意义，
则x-1≠0，
解得x≠1．
故选A．
If it is quite _______ to you, I will visit you next Tuesday.
A．convenient
B．fair
C．easy
D．comfortable
Which of the following market structure characterized that a large number of competitors produce (slightly) differentiated products with low barriers to entry（）
A. Perfect competition.
B. Monopolistic competition.
C. Oligopoly.
