The principal, having increased the number of teachers in the school,

OFFICIAL EXPLANATION

THE PROMPT

THE OPTIONS
• Grammatical but nonsensical
There are no grammar errors, but the meaning is silly.
→ If the principal has increased the number of teachers in the school, then why is he [now] being accused of maintaining a poor ratio of students to teachers?

• Meaning / Logic -- the sentence is illogical. We need a contrast word to highlight that the situation is ironic and weird.
No such contrast word exists.

ELIMINATE A

• Strange timing / cause and effect are poorly rendered
→ Is the principal increasing the number of teachers at the school at the same time that he is "still" being criticized?
The timing is confusing.

• The word however
→ almost always on the GMAT, however joins two full clauses, follows a semicolon, and is followed by a comma, this way:
The leaders of certain countries are stone cold killers; however, they are tolerated because they control resources upon which the rest of the world depends, albeit unwisely.

→ if you see however without a semicolon and however means "nonetheless" rather than "in whatever way," it should be flanked by commas—meaning, a comma before and a comma after. This sentence is missing a comma after however.
Punctuation is rarely dispositive, but the GMAT is fairly strict about the three ways however is used, about which you can read here, in this short article..
ELIMINATE B

• ungrammatical: the subject (principal, he, or she) must be repeated after the comma because what comes after the comma is a full clause
ELIMINATE C

• This option looks promising—finally the option makes the irony or paradox clear
• Although and still are not redundant contrast words.
→ Still can mean "up to the present moment/ even now" or "nevertheless."
→ In this option, still means even now and does not clash with although.

Correct: Although the Ukrainians have been promised more heavy artillery quite a few times, the embattled defenders still have not received much of that particular kind of help, badly needed to defend against Putin's vicious attack.

• The time frame in this option D makes sense
ALthough the principal has (just) increased the number of teachers, he is still being attacked . . .
KEEP

• Redundancy (and problems with double contrast)
In this case, although and yet mean the same thing, are redundant, and create an illogical sentence.

The answer is D.

COMMENTS

Analysis is good. Nice work.