Why Capacitive reactance is Xc = 1/(2πfC), so frequency sits in the denominator: double the frequency and the reactance is halved. Physically, a capacitor has to charge and discharge, and at higher frequencies the polarity reverses so quickly that more current flows for the same voltage, which is the same as saying the opposition is lower. Note that reactance depends only on frequency and capacitance, not on how large the applied voltage is.
Watch out The choice saying reactance rises with frequency describes an inductor, where XL = 2πfL. The amplitude choices are wrong because reactance is independent of signal level in an ideal component.
C and f are both on the bottom of 1/(2πfC): higher frequency, lower Xc. Capacitors pass highs, block DC.