A particle moves along $x$ -axis in such a way that its position coordinate $(x)$ varies with time $(t)$ according to the expression $x=2-5 t+6 t^{2}$. Its initial velocity is
a. $-3 \mathrm{~m} / \mathrm{s}$
b. $-5 \mathrm{~m} / \mathrm{s}$
c. $2 \mathrm{~m} / \mathrm{s}$
d. $3 \mathrm{~m} / \mathrm{s}$