Which one of the following gives a yellow precipitate with iodine and $NaOH$ solution?

Three rods each of length $L$ and mass $M$ are placed along $X$,$Y$,and $Z$-axes such that one end of each rod is at the origin. The moment of inertia of this system about the $Z$-axis is:

The products formed when heavy water is reacted with magnesium nitride are:

The magnifying power of a telescope with tube length $60 \ cm$ is $5$. Then the focal length of its eyepiece is: (in $cm$)

Which of the following compounds lacks iron?

The pulleys in the diagram are all smooth and light. The acceleration of $A$ is $a$ upwards and the acceleration of $C$ is $f$ downwards. The acceleration of $B$ is