The answer is choice D because we plug in something like x = pi/4 and it leads to
y = cos(2x)
y = cos(2*pi/4)
y = cos(pi/2)
y = 0
Use the unit circle to see why cos(pi/2) = 0.
Since we get y = 0 as a result, this shows x = pi/4 is one of the x intercepts.
You'll also get y = 0 if you plug in x = 3pi/4, x = 5pi/4, and x = 7pi/4. All of these values are on the interval [tex]0 \le x < 2\pi[/tex]
