I have an equation

$\displaystyle dS_{i}(t)=S_{i}(t)(\mu_{i}(t)dt+\sum^{d}_{k=1} \sigma_{ik}dW_{k}(t)) $

We have a filtraiton $\displaystyle G_t$

Show that the expectation of $\displaystyle \frac{S_{i}(t+\triangle)-S_{i}(t)}{S_{i}(t)} |G_{t}=\mu_{i}(t)\triangle$