Mastering an array of technical skills?

Business English Lesson, Advanced Level

ESL/EFL Test #95 [color=blue]“Corporate Policy (3)”, question 5

He must master an of technical skills.

(a) array
(b) arrow
© accord
(d) aridity

Business English Lesson, Advanced Level

ESL/EFL Test #95 [color=blue]“Corporate Policy (3)”, answer 5

He must master an array of technical skills.

Correct answer: (a) array

Your answer was: [color=green]correct
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Can you kindly explain the meaning of the sentence?
Thank you
Ian

I think it’s just a phrase “array of skills”. That’s what is often said.