Which of the following hormones contains iodine?

$\cos ^2\left(\frac{\pi}{6}+\theta\right)-\sin ^2\left(\frac{\pi}{6}-\theta\right)$ is equal to

If the water falls from a dam into a turbine wheel $19.6\, m$ below,then the velocity of water at the turbine is ............. $m/s$ $(g = 9.8\,m/s^2)$.

Which of the following plants is commonly used as green manure?

Chloramphenicol and erythromycin (broad spectrum antibiotics) are produced by

The centre of the circle $r^2-4r(\cos \theta+\sin \theta)-4=0$ in Cartesian coordinates is