1, be up to means "engaged, busy", followed by nouns, pronouns or -ing.

All of us are doing good deeds. All of us are doing useful things.

Go and see what these naughty boys are doing. Go and see what these naughty children are doing.

It's up to sb. Do sth. It means "someone should do something".

It is often used as a formal subject.

It's up to me to get the four of us moving. I'll get the four of us moving.

It's up to sb. It means "it's up to someone to decide and follow someone"

It's up to your brother whether we go to the park or not.

Indian or Chinese food? It's up to you. Indian or Chinese food? It's up to you.

4, be up to means "competent, suitable, suitable", mostly used in negative sentences or interrogative sentences.

Li Ping is not up to his job. Li Ping is not up to his job.

Do you think she can do it alone? Do you think she can finish it alone?

5, be up to "means: comparable, comparable."

Smith's new book is not as good as his last one. Mr Smith's new book is not as good as his previous one.

Extended information related sentences:

1, yes? Up? Where to? Him? Where to? Resolve? This? problem ?

This problem should be solved by him.

Now you can use this tool, how to use it depends on yourself. ?

Since this tool is useful to you, how to use it is entirely up to you.

3. When I write a book, I write a book for myself; The response depends on the reader. ?

When I write a book, I write it for myself, but the reader's reaction depends on the reader.

I think everyone in the movie has a reason to do what they do, which I respect very much. So in a sense, judgment depends on you. ?

I think everyone in the film has a reason to do that, and I respect them, so the question of judgment depends on your attitude to some extent.