Answer:
A. a wave with an amplitude of 1.0
Step-by-step explanation:
The intensity (and therefore the loudness) of a sound wave is proportional to the amplitude of the wave itself: the larger the amplitude, the louder the sound, and the smaller the amplitude, the weaker the sound.
In this problem, we are given 4 different waves with different amplitudes. Among the choices, we see that wave A has the largest amplitude (1.0), therefore this will be the wave with greatest intensity, so the loudest sound wave among the choices.