Identify the singular subject pronoun in the sentences given below:
I am reading some books.

The correct answer is: I

'I' is the singular subject pronoun. The pronouns 'I' and 'we' are personal pronouns of the first person. 'I' is the singular first person subject pronoun, whereas 'we' is the plural first person subject pronoun. In the given sentence, ‘I’ is the subject of the verb ‘am reading’.