Tonoplast is

Tonoplast is Correct Answer Outer membrane of vacuole

Tonoplast is outer membrane of vacuole.
The vacuole is a membrane-bound organelle that is present in plant and fungal cells and some protist, animal and bacterial cells.
A vacuole is surrounded by a membrane called the tonoplast and filled with cell sap. In 1885, de Vries named the vacuole membrane as tonoplast. It is the cytoplasmic membrane surrounding a vacuole, separating the vacuolar contents from the cell's cytoplasm.