The noun can be substituted by pronoun to form a meaningful sentences when writing a task or speaking to readers.
For example, in the above case, “The boy” can be replaced by pronoun “he” watched the lights in the house go off. This forms a correct sentence without grammar error, where boy is a male.
Thus, the options (c), (b) and (a) are incorrect.
For example, in the above case, “The boy” can be replaced by pronoun “he” watched the lights in the house go off. This forms a correct sentence without grammar error, where boy is a male.
Therefore, the correct option is – d. he.