d
(d) $y = 4\sin 2\pi \left( {\frac{t}{{0.02}} - \frac{x}{{100}}} \right)$.
Comparing this equation with $y = a\sin 2\pi \left( {\frac{t}{T} - \frac{x}{\lambda }} \right)$
$v = \frac{{{\rm{Co - efficient \,of\, }}t}}{{{\rm{Co - efficient\, of\, }}x}} = \frac{{1/0.02}}{{1/100}}$