Question

The student said to the beacher, "I bought a black pem
yesterday".​

Answer 1

$\huge\pink{\tt{\underline {Required\:Answer}}}$

The student told the teacher that he had bought a black pen the previous day.

Extra Information ↴

• Reporting verb is changed according to the form and sense of the sentence.
• Inverted commas are removed in the Indirect-speech.
• Connecting word is used in the beginning of the reported speech.
• Verb of the reported speech is changed according to form and sense of the sentence.
• Persons of the reported speech are changed.
• Words showing nearness, time or place are changed.

According to the rules, if the direct speech is in the simple past tense, then it is usually converted into the past perfect tense in indirect speech. 'Yesterday' is changed into 'the previous day'.