For a particular reaction,the variation of the rate constant with temperature is given by $\ln k_t = \ln k_0 + \left( \frac{\ln (2.5)}{10} \right) \times t$ $(t \geqslant 0 \, ^{\circ}C)$. Here,$k_0$ is the rate constant at $0 \, ^{\circ}C$ and $k_t$ is the rate constant at $t \, ^{\circ}C$. The temperature coefficient of the reaction,assuming that the rate constant increases by the same factor for every $10 \, ^{\circ}C$ rise in temperature,is:

• A
  $2$
• B
  $2.5$
• C
  $5$
• D
  $0.4$