孟德尔在豌豆杂交实验中,发现问题和验证假说所采用的实验方法依次是( )
Mr. Lin gave Lily some good advice on how to ____ with the problem.
①﹣20+(﹣14)﹣(﹣18)﹣13
②(﹣1)÷(﹣1 23 )×3
③6÷(﹣ 12 + 13 )
④﹣16﹣|﹣5|+2×(﹣ 12 )2.