investigators concluded that human failure was not responsible for airplane
crash last Augst,and since that time new and more stringent rules for
identifying and reporting mechanical problem have beeb in effect.that accounts
for the fact that reports of airplane mechanical problem have increased in
frequency by 50 percent since last August
which one of the following is an assumption buderlying the argument
1 airplane travel is still safe,despite the inceasing in the reproted
mechanical problem
2mechanical problem have inceased dramatically since last Augest
3mechanical problem in airplane have not inceased by 50% since last Augest
4airline are less reluctant to report mechanical problem than they previously
were
5mechanical problem have become easier to detect since last August
请高手指点哪个是对了,我没太搞懂逻辑关系 | 
