What's the difference between its and it's?
Its is posessive and it's is a contraction of "it is".
When should I use "who's" versus "whose"?
Use "who's" (who is/who has) when identifying someone or something; use "whose" to show possession.
_____ (Its / It's) going to rain later today.
It's going to rain later today.
What's the difference between their, there and they're?
Their is possessive, there refers to location and they're is a contraction of "they are".
When should I use "may" and "might"?
"May" suggests a higher possibility or permission; "might" suggests a lower possibility or uncertainty.
She laid the book _____ (on / in) the table.
She laid the book on the table.
What's the difference between affect and effect?
Affect is usually a verb meaning to influence, effect is usually a noun meaning the result.
When should I use "less" and "fewer"?
Use "fewer" with countable nouns and use "less" with uncountable nouns.
There are _____ (less / fewer) apples in the basket than yesterday.
There are fewer apples in the basket than yesterday.