Correct Answer: (c) "Amit, please stop taking tranquillizers without consulting the doctor," said Amar.
Note: (c) "Amit, please stop taking tranquillizers without consulting the doctor," said Amar. (Correct)
(a) "Amit,please stop taking tranquillizers without consulting the doctor," Amar was advising (Incorrect Reported Verb)
(b) Amit said to Amar, "Please stop taking tranquillizers without consulting the doctor." (Incorrect speaker and listener)
(d) Amar says to Amit," Please consult the doctor before taking tranquillizers." (Incorrect Reported verb and meaning has changed)