When do must be true question, i often draw a chart and it helps me a lot. If A, then B = A ->B. And we know contrapositive is correct. It means Not B -> Not A is correct. So apply this rule to this question:
A= a motor is sound-insulated
B= it is quiet enough to use in home appliances
C= it can be used in institutional settings
So, rewrite the stimulus we have: A - B; B->C ; and no motor manufactured byy.... is not B.
Answer analysis:
(A) If a motor can be used in institutional settings,
...
A= a motor is sound-insulated
B= it is quiet enough to use in home appliances
C= it can be used in institutional settings
So, rewrite the stimulus we have: A - B; B->C ; and no motor manufactured byy.... is not B.
Answer analysis:
(A) If a motor can be used in institutional settings,
...
