Answer : 3. "इंजीनियर"
Explanation :

A is a Hindu, B is a Sikh, E is a Muslim. Now, the doctor is a Christian and D is a cloth merchant. So, C is a Christian and D is a Hindu.

II.)   D stays in locality S. E stays in locality R. Now, one businessman i.e. D and the lawyer stay in S. C is a doctor, stays in locality P. Clearly, A stays in locality Q.

III.)  Clearly, A is a factory owner, B is a lawyer, C is a doctor, D is a cloth merchant and E is an engineer.

	A	B	C	D	E
Profession	Factory Owner	Lawyer	Doctor	Cloth merchant	Engineer
Religion	Hindu	Sikh	Christian	Hindu	Muslim
Locality	Q	S	P	S	R

IV.)  B, the lawyer, is oldest. A, the factory owner, is the youngest. D, the cloth merchant lies between doctor and lawyer i.e. B and C in age.

So, age wise sequences : B > D > C > E > A.
Hence, E lies between A and C. E is an engineer.