Final answer:
The function sec(x) is undefined when the cosine of x equals zero, which occurs when x is an odd multiple of π/2. Therefore, the correct answer is option C) 2.
Step-by-step explanation:
The function sec(x) is undefined for values of x that make the cosine function equal to zero. In other words, sec(x) is undefined when the cosine of x equals zero. This occurs when x is an odd multiple of π/2, such as π/2, 3π/2, 5π/2, etc. So, the correct answer is option C) 2.