What is true about nodes and antinodes of a standing wave

a.) they decrease in number with time
b.) they remain in a fixed position
c.) their position keeps changing with time
d.) they increase in number with time

This should // 
these are the points that undergo the maximum displacement during each vibrational cycle of the  standing wave. in a sense, these points are the opposite ofnodes , and so they are called  antinodes . a  standing wave   pattern always consists of an alternating pattern of  nodes and antinodes .

Distance^2= yellow line ^2 (see picture) = 30^2 + 49^2so distance = squareroot of (300^2 +49^2)i dont know if this is how to solve it, but i cnt think of another way