Correct: B
We know that 1/sec A is equivalent to cos A.
The cosine function, cos A, has a defined range of values. For any angle A, the value of cos A always lies between -1 and 1, inclusive.
That is, -1 ≤ cos A ≤ 1.
Therefore, the maximum value that cos A (or 1/sec A) can attain is 1.