Questions

Molecular compounds are those with covalent bonds between the elements and those elements are typically non metals.

Here in the given options, Ar is an element. NaI has an ionic bond. Hence, N2O4 has a covalent bond between the two non metals and is a molecular compound.

Protein synthesis at the ribosome is immediately preceeded by the transcription process.

Pass input to XOR and give their outputs to OR gate, if your output is 0 both 8-bit signals are same.

OR

Pass input to XNOR and give their outputs to AND gate, if your output is 1 both 8-bit signals are same. 

Before transferring the fish, the position is the man with the fish and the bucket of water. After transferring the position is: the man without the fish, but the fish inside the water in the bucket. Thus to know  whether there is any change in weight, it is enough to consider whether there is any change in weight when the fish in air is transferred into the water. The answer is there is no change as when in water though it loses weight due to upthrust of water on it, the level of water increases and exerts an equal force at the bottom.So, (c) is correct.