Difference between impervious and impenetrable

[Guest]

Test No. incompl/advan-88 "GMAT Verbal Quiz (11)", question 4

Fortunately she took no notice of the reviews of her acting and was quite ......... to some of the more sarcastic comments.

(a) important
(b) impenetrable
(c) immediate
(d) impervious

Test No. incompl/advan-88 "GMAT Verbal Quiz (11)", answer 4

Fortunately she took no notice of the reviews of her acting and was quite impervious to some of the more sarcastic comments.

Correct answer: (d) impervious

Your answer was: incorrect
Fortunately she took no notice of the reviews of her acting and was quite impenetrable to some of the more sarcastic comments.
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I don't understand the difference between "impervious" and "impenetrable". Could you cite a few examples?

[Alan]

Impervious to in this sentence means not affected by/not sensitive to and is used in a figurative sense in a passive way. Impenetrable means that you cannot penetrate it such as very thick rock/stone and is therefore used in an active way.
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