Correct Answer: "It is raining heavily. Please drive slowly," I said to my driver.

Solution : The third option is the correct choice.

Direct speech is a form of speech or writing where the actual words spoken by a person are quoted within quotation marks and attributed to the speaker.

The steps of conversion are as follows:

• The reporting verb "told" is changed to "said".
• The past continuous tense "was raining" is changed to the present continuous tense "is raining".
• The infinitive form of the verb is changed to the base form, making the sentence imperative with the help of the word "please" as in the case of a request.
• The words of the speaker are enclosed in inverted commas.

Therefore, the correct answer is: "It is raining heavily. Please drive slowly," I said to my driver.