Any food that is not sterilized and sealed can contain disease-causing bacteria. Once sterilized and properly sealed,...

Mehran on May 26, 2016

@Mia6 you have plenty of time to diagram this stimulus and find the correct answer.

The only two statements that can be diagrammed here are the first two:

"Any food that is not sterilized and sealed can contain disease-causing bacteria."

not ST&S ==> can CDCB
cannot CDCB ==> ST&S

"Once sterilized and properly sealed, however, it contains no bacteria."

ST&S ==> not B
B ==> not ST&S

The last sentence is a quantifier but it does not connect with our S & N statements so no need to write out.

The stimulus is a statement of facts so we can proceed to the question stem, which asks us to find the answer choice that must be true.

(A) All food preserved by an acceptable method is free of disease-causing bacteria.

This is not correct as the stimulus tells us that there are many different acceptable food-preservation techniques, some of which do not involve sterilizing and sealing (e.g. slowing the growth of disease-causing bacteria) and that any food that is not sterilized and sealed can contain disease-causing bacteria.

(B) Preservation methods that destroy enzymes that cause food to spoil do not sterilize the food.

Again, we have no idea. All we know is that some of the techniques may also destroy natural food enzymes that cause food to spoil or discolor quickly, but we do not know whether or not these techniques include sterilization.

(C) Food preserved by a sterilization method is less likely to discolor quickly than food preserved with other methods.

Nothing in the stimulus supports this statement.

(D) Any nonsterilized food preserved by an acceptable method can contain disease-causing bacteria.

This must be true as it is directly supported by the first sentence, i.e. "Any food that is not sterilized and sealed can contain disease-causing bacteria" and the fact that there are acceptable food preservation techniques that do not involve sterilizing and sealing.

(E) If a food contains no bacteria, then it has been preserved by an acceptable method.

Again, not supported. This stimulus is about preserved food. Fresh food could contain no bacteria even though it has not been preserved by an acceptable method.

Hope this helps! Please let us know if you have any other questions.

Julie-V on August 21, 2019

I was wondering if the first sentence is supposed to be read as not sterilized AND NOT sealed, or is the "not" supposed to go to sterilized only. Thanks!

Irina on August 21, 2019

@Julie,

The first sentence can be diagrammed either as :

~(ST & S) - > CB
or

~ ST v ~S -> CB

These are logically equivalent, so to answer your question, NOT refers to both -sterilized and sealed.

Let me know if you have any further questions.

the66guy on October 26, 2021

To write the contrapositive we are supposed to reverse and negate the statement. "And" turns to "or" and vice-versa. Why wasn't this done on the first sentence and Mehran's explanation
(not ST&S ==> can CDCB
cannot CDCB ==> ST&S)?

Ravi on February 4, 2022

You're right that you reverse and negate statements when doing contrapositives with "and" and "or" when they are separating two distinct statements. However, in this case, you can treat sterilized and sealed as one term/item, which is why Mehran's translation is correct.