What is the meaning of “be up to someone”?
Native speaker’s answer
Rebecca
"It is up to all of us" means that everyone needs to be involved in order to achieve a common goal. If a task is "up to someone" it means that one specific person is the only one who can complete a task. "It is up to you" can also mean to make a decision. Ex: It is up to you to make things right. Ex: It is up to all of us to change our company. Ex: A: Should I go to the dance tonight? B: It is up to you.