Let \( f(x)=3\sin^{4}x+10\sin^{3}x+6\sin^{2}x-3, \ x \in \left[-\dfrac{\pi}{6},\dfrac{\pi}{2}\right] \). Then, \( f \) is:
decreasing in \( \left(-\dfrac{\pi}{6},0\right) \)
increasing in \( \left(-\dfrac{\pi}{6},\dfrac{\pi}{2}\right) \)
decreasing in \( \left(0,\dfrac{\pi}{2}\right) \)
increasing in \( \left(-\dfrac{\pi}{6},0\right) \)