The number of hydrogen atoms in the given compound is:

The electrophile $NO_2^+$ reacts with which of the following compounds? In which case will $NO_2^+$ attack at the meta position?
$(I)$ $C_6H_5-CCl_3$
$(II)$ $C_6H_5-NO_2$
$(III)$ $C_6H_5-CHO$
$(IV)$ $C_6H_5-O^-$

Which of the following statements is incorrect for the nitration of an aromatic compound?

The number of disubstituted products of benzene is

The product formed when acetylene is passed through a red-hot tube is:

Which of the following reactions is correct?