Choose the correct indirect speech form of the given statement.
A clever mouse said to all, “Let’s bell the cat.”
a) A clever mouse proposal all that they should bell the cat
b) A clever mouse proposed to all that they should bell the cat
c) A clever mouse suggested that they must bell the cat
d) A clever mouse suggested all that they would bell the cat

Hint: In indirect speech, the present tense changes to past tense, along with other necessary changes. So, direct speech should be changed accordingly. It will never be repeated exactly as the subject said it.

Complete answer:
In grammar, there are two kinds of speech - Direct and Indirect.
In direct speech, we use quotes to repeat the exact thing an individual said. However, in indirect speech, the direct quote is said in the third person, and so the quotation marks are removed. In order to change the direct speech into indirect speech, we must change the tense of the sentence, and make the necessary punctuation changes.
When we want to report something someone said without speech marks, we use indirect speech. It is also called reported speech.
When you convert a sentence from direct to indirect speech, the tense changes. From direct to indirect, the tense changes from present to past. The reported speech cannot contain any questions, so the sentence quotations should not start with a verb.

Now, we know what we are looking for. Let’s look at the given options:

option ‘a’ - In this option, there is no verb used. This impacts the reported speech, as it does not look like a completed action. This is not the required answer. So, this is an incorrect option.
option ‘b’ - In this option, the correct verb form is used, so the action is completed. No part of the sentence is missing. This sentence is the correct indirect speech. This is the required answer. So, this is the correct option.
option ‘c’ - In this option, a part of the sentence is missing, and an incorrect helping verb is used. This is not the required answer. So, this is an incorrect option.
option ‘d’ - In this option, the sentence is grammatically incorrect, as a preposition is missing, and an incorrect helping verb is used. This is not the required answer. So, this is an incorrect option.

Note:
Break the sentence into separate parts and try to convert each part into indirect speech. Changing individual parts will make sure that you do not miss a part of the sentence. Make sure there is no question being asked.