The correct option is A \N
As we discussed in the videos that d3ydx3 is nothing but third successive derivative of y. i.e,
ddx(ddx(dydx))
So for the function y = sinx,
dydx=cosx
ddx(dydx)=−sinx
ddx(ddx(dydx))=−cosx=d3ydx3
At x=π2,
d3ydx3=−cosπ2=0 which is the correct answer.