Which of the following is not a secondary messenger?

Decomposers are

$A$ telescope has an objective lens of focal length $150 \ cm$ and an eyepiece of focal length $5 \ cm$. If a $50 \ m$ tall tower at a distance of $1 \ km$ is observed through this telescope in normal setting,the angle formed by the image of the tower is $\theta$,then $\theta$ is close to..... (in $^{\circ}$)

Which of the following substances will not give a borax bead test?

$A$ three-digit number $n$ is such that the last two digits are equal and differ from the first digit. The number of such $n$'s is:

The intensity of the magnetic induction field at the centre of a single turn circular coil of radius $5 ~cm$ carrying a current of $0.9 ~A$ is: