Electrophilic substitution reaction of chlorobenzene:
In electrophilic substitution reactions, a hydrogen atom in the benzene ring is replaced by an electrophile. Chlorobenzene is an aromatic compound with a chlorine atom attached to the benzene ring. Let's understand the role of the chloro group in this reaction.

Option A: Activates the ring by inductive effect:
The inductive effect is the polarization of electron density in a molecule due to the presence of an electronegative atom or group. Chlorine is more electronegative than carbon, so it can withdraw electron density from the benzene ring through the sigma bond. This withdrawal of electron density could potentially deactivate the ring towards electrophilic substitution reactions. Therefore, option A is incorrect.

Option B: Acts as meta directing group:
In electrophilic substitution reactions, substituents on the benzene ring can direct the incoming electrophile to specific positions on the ring. Chlorobenzene is a weakly deactivating ortho/para directing group due to resonance effects. However, it does not strongly direct the incoming electrophile to the meta position. Therefore, option B is incorrect.

Option C: Increases electron density on the benzene ring:
The chlorine atom in chlorobenzene is an electron-withdrawing group due to its high electronegativity. It withdraws electron density from the benzene ring through the sigma bond. This withdrawal of electron density decreases the electron density on the ring, making it less reactive towards electrophilic substitution reactions. Therefore, option C is incorrect.

Option D: Gives ortho/para substituted product:
Although chlorobenzene is a weakly deactivating group, it still directs the incoming electrophile to the ortho and para positions on the benzene ring. This directing effect is due to the resonance stabilization of the intermediate carbocation formed during the reaction. Therefore, option D is correct.

Conclusion:
In the electrophilic substitution reaction of chlorobenzene, the chlorine atom acts as a weakly deactivating ortho/para directing group. It directs the incoming electrophile to the ortho and para positions on the benzene ring, giving ortho/para substituted products.