是has还是have?A lot of advice has/ have been offered by people?

填has,advice是不可数.
lot表示很多,多数.
一般用于a lot of,lots of a lot of 后面接可数名词和不可数名词均可,
接可数名词时谓语用复数,
接不可数名词时,谓语用单数.