A sentence has been given in Direct speech. Out of the four given alternatives, select the one which best expresses the same sentence in Indirect (reported) speech: The teacher said, “The moon goes round the earth.”

Introduction / Context:
This question evaluates your understanding of Direct and Indirect speech, particularly when reporting universal truths or scientific facts. The original sentence is a statement about an astronomical fact: “The moon goes round the earth.” When such general truths are reported, the tense of the verb in the reported clause is usually not changed, even if the reporting verb is in the past tense.

Given Data / Assumptions:

• Direct speech: “The teacher said, ‘‘The moon goes round the earth.’’”
• Reporting verb: said (simple past).
• Reported clause: “The moon goes round the earth” – a scientific fact.
• We need to convert this into Indirect speech without distorting the meaning.

Concept / Approach:
When we change a statement from Direct to Indirect speech, we normally backshift the tense of the reported clause if the reporting verb is in the past. However, an important exception occurs with universal truths and permanent facts: their tense is not changed, because the fact remains true at all times. Therefore, “goes round” remains goes round in the reported clause. We introduce the clause with that after said, resulting in: “The teacher said that the moon goes round the earth.”

Step-by-Step Solution:
Identify the reporting verb: said, indicating a statement, not a question.Identify the nature of the reported statement: a scientific fact about the moon and the earth.Apply the rule: for universal truths, do not change the present simple tense in reported speech.Form the reported clause: that the moon goes round the earth.Combine with the reporting verb: “The teacher said that the moon goes round the earth.”

Verification / Alternative check:
Check each option against these rules:Option (a): “The teacher said that the moon goes round the earth.” – correct reporting verb, correct conjunction that, and present simple goes round retained for a scientific fact.Option (b): “The teacher asked whether the moon goes round the earth.” – uses asked and whether, which is for questions, but the original sentence is not a question.Option (c): “The teacher informed about moon going round the earth.” – awkward structure, missing the article the and not a standard reported speech form.Option (d): “The teacher asked whether moon goes round.” – incorrect reporting verb and incomplete clause (missing “the earth”).Therefore, only option (a) correctly follows the rules of reported speech.

Why Other Options Are Wrong:
Option (b) treats the original statement as if it were a yes/no question by using asked and whether, which changes the sentence type. Option (c) uses informed about, an unnatural collocation here, and leaves out important words while also not clearly forming a subordinate clause with that. Option (d) removes “the earth”, breaking the meaning of the scientific fact, and also incorrectly uses asked and whether, again suggesting a question rather than a statement.

Common Pitfalls:
A frequent mistake is to backshift the tense of a universal truth to past simple (“went round”) or to change the reporting verb type. Another mistake is to ignore the structure of reported statements and use verbs like informed or asked incorrectly. A reliable exam strategy is: if the original statement is a scientific fact or universal truth, keep the present tense in indirect speech and use a neutral reporting pattern like said that. This quickly leads you to the correct answer here.

Final Answer:
The correct Indirect speech form is: The teacher said that the moon goes round the earth.