Meaning of "abstruse"

[Jonas Ferreira]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #91 "Advanced Vocabulary", question 5

I find these mathematical puzzles too ......... and prefer the more straightforward type.

(a) abject
(b) abortive
(c) abounding
(d) abstruse

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #91 "Advanced Vocabulary", answer 5

I find these mathematical puzzles too abstruse and prefer the more straightforward type.

Correct answer: (d) abstruse

Your answer was: incorrect
I find these mathematical puzzles too abounding and prefer the more straightforward type.
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What does abstruse mean? Does it mean "hard" to be solved?

Jonas Ferreira

[Yankee]

Hi Jonas

Abstruse means 'hard to understand or penetrate'.
.