present simple and adding s after the Sentence

Question

why do i have to add s after the word causes in the follow Sentence i know that it is because causes is present simple but when i look at the grammar it say i/we/you/they take drive/work/do etc. he/she/it take drives/works/does etc but the Sentence dose not start with any of them

Bad driving cause(s) many accidents.

Answer 1

Driving here is a gerund—an -ing form of a verb which acts as a noun.

You can tell it's acting as a noun because

• it is modified with an adjective, bad, rather than an adverb, badly
• it acts as the subject of the sentence

Since it is the subject, and singular, it takes the 3rd person singular form of the verb: causes. It's not just 3rd-person pronouns which take that form: any 3rd-person singular subject takes that form.

• John causes many accidents.
• My nephew causes many accidents.
• Carelessness causes many accidents.