A 100 Hz sinusoidal wave is travelling in the positive x-direction along a string with a linear mass density of $3.5\times {10}^{-3}kg{m}^{-1}$ and a tension of 35N. At time t=0, the point x=0 has zero displacement and the slope of the string is $\raisebox{1ex}{$\pi $}\!\left/ \!\raisebox{-1ex}{$20$}\right..$ Then select the wrong alternative.