Bunuel wrote:
Of the thirteen samples of skin cells, only two, having intact cell walls, could be used by the team of researchers for an analysis of the effects of various chemicals on healthy skin.
A. Of the thirteen samples of skin cells, only two, having intact cell walls,
B. Of the thirteen samples of skin cells, only two, which had intact cell walls,
C. Only two of the thirteen samples of skin cells, with cell walls that were intact
D. Only two of the thirteen samples of skin cells, which has intact cell walls
E. Only two of the thirteen samples of skin cells, being that their cell walls are intact
Responding to a PM:
The main debate here is between (A) and (B), so I will address the split between these 2.
In both (A) and (B), the modifiers are non-essential modifiers referring to "
only two (of the thirteen samples of skin cells)". However, the tense in the non-underlined portion of the sentence is simple past, "
could be used". And while "could" could theoretically be used in the present tense to indicate a hypothetical,
the more logical meaning and/or interpretation of this sentence is that the sentence is reporting [on] some event (analysis) performed by the team of researchers sometime in the past, as a result of which the (what would have been a) "
can" in direct speech changes to "
could" in indirect/reported speech. Hence, there should be concord with regard to the tense of the non-essential modifier as well. Option (B), by using a simple past tense in "
had", accurately conveys this idea.
If, however, the non-underlined portion of the sentence were describing an event in the present day, then a present participle "having", as in Option (A), would have been preferable, as it makes it look as though the two cells
are currently having intact cell walls. And while it is true that the present participle, in and of itself, does not indicate the tense as a finite verb does, in this case, the most logical interpretation is that "having" refers to the idea of the cells' possessing or owning something in the present day. Hence this is incorrect and can be eliminated.
The other options are fairly easy to eliminate -- among other things, option (C) should have a comma after "were intact" to ensure that there is an independent verb for the subject "
Only two"; option (D) has a missing comma after the non-essential modifier, plus the "has" is incorrect as well (since "skin cells" are plural); and option (E) replicates the missing comma error in addition to, in this context, a hugely avoidable, awkward "being".
Therefore, for all the above-mentioned reasons, Option (B) is our best choice.