Explanation:

Here’s what’s going on in that first blank:

- The sentence is: "One of the most basic (1)______ of a human is food."

- We want a noun here that means “something people must have.”

Let’s size up your options:

1. needed – This is a past participle/adjective, not a noun.

2. needer – Not a real word; you won’t see this in proper English.

3. needful – An adjective, not a noun. You don’t say “the needful of a human.”

4. needs – This is the plural noun form, perfect for “the most basic needs of a human.”

Correct Answer: option 4 – needs

So, "One of the most basic needs of a human is food" just works. It’s how real people talk and write. The other options are just off grammatically.