Like embryonic germ cells, which are cells that develop early in the

As it's written, the sentence makes a comparison between embryonic germ cells and embryonic stem cells. The structure of the sentence supports this comparison grammatically.

Let's start by eliminating any answer choices that have straightforward grammatical errors.


This choice introduces an error by introducing a comparison of two things that definitely aren't intended to be compared. If we choose (C), then we'll end up with the following erroneous construction:

Like embryonic germ cells, which are cells that develop early in the formation of the fetus and that later generate eggs or sperm, in embryonic stem cells there is the ability to develop into into different kinds of body tissue.

"Embryonic germ cells" cannot be compared to "in embryonic stem cells." They must be compared to "embryonic stem cells." So let's eliminate (C).


We'll eliminate this choice for the exact same reason we eliminated choice (C): It breaks the author's intent to compare one type of cell to another type of cell.

"Embryonic germ cells" cannot be compared to "the ability," so eliminate (D) and move on.


We'll eliminate this choice for the exact same reason we eliminated choice (C) and choice (D).

"Embryonic germ cells" cannot be compared to "the ability," so eliminate (E).

OK! Now that we've gotten the easy stuff out of the way, let's get back to (A) and (B).


Here, we see that the underlined portion itself isn't quite right. We typically use the phrase "the ability of _________________" when an ability belongs to whatever is filling in the blank:

• In their efforts to develop a new kind of skin graft, scientists have harnessed the ability of lizards to regenerate tails.
• The abilities of Superman are virtually limitless.

But in this sentence, we're told that "embryonic stem cells have the ability of developing themselves into different kinds of body tissue." This choice of preposition ("of") isn't appropriate for what the author means. The author means that embryonic stem cells can develop themselves into different kinds of body tissue, not that embryonic stem cells have the same kind of ability that "developing themselves" has.

You could also argue that there's no good reason to say "developing themselves." It's probably enough just to say that the cells "develop into" some other type of cell, so "developing themselves into" another type of cell is probably redundant.

So we have a couple of good reasons to eliminate (A).


This looks good! It's exactly the same as the original underlined portion, except that the preposition error has been fixed, and the potential redundancy of "developing themselves has been eliminated.

So (B) is our winner.