Which one of the following phrases, if substituted for the word "head" in line 47, would LEAST change the meaning of ...

Shiyi-Zhang January 25, 2019

Could someone explain this question to me? Thanks!

Ravi January 26, 2019

@Shiyi-Zhang,

Happy to help.

The question is asking us which one of the following phrases, if
substituted for the word "head" in line 47, would LEAST change the
meaning of the sentence? In other words, we're looking to pick an
answer that is a synonym of the word "head."

The key to getting this question correct is recognizing that the
passage defines the term "head " for us in the first paragraph in line
26, where we're told that "head" is the pressure inside the pump.

The phrase that contains "head" from line 47 reads, "significant
reductions in head can occur as it operates." We know from earlier in
the passage that "head" means the pressure inside the pump, so we're
looking for an answer that either says this or is a paraphrase of
this.

(A) says the flow inside the pump. We're looking for the pressure, not
the flow. This is out.

(B) says the volume of oil inside the pump. We're looking for the
pressure of the pump, not the volume of oil. This is out.

(C) says the volume of gas inside the pump. We're looking for the
pressure of the pump, not the volume of gas. This is out.

(D) says the speed of the impeller moving the crude. We're looking for
the pressure of the pump, not the speed of the impeller moving inside
the crude. This is out.

(E) says the pressure inside the pump. This is almost exactly the
definition of "head" we were given in line 26. This is the correct
answer.

Does this make sense? Let us know if you have any more questions!