Graphs of Sine and Cosine · Medium problem

$2\cos\!\left(\tfrac{\pi}{6}t\right)-4$

$2\cos\!\left(\tfrac{\pi}{6}t\right)+5$

$2\cos\!\left(\tfrac{\pi}{6}t\right)+4$

$2\cos\!\left(\tfrac{6}{\pi}t\right)+4$