BB Test 20 TC

why is this question not a double possibility ?? and How do we apply math strategy??
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for the above question[4] why cant the answer choice be C treacherous and safeguard??

Is the answer D?
The answer is not C because although the safeguards fits the second blank, the word treacherous is a very extreme in this case.

yea the answer is D
Ohkay gotcha!!!