The diagram shows apparatus for measuring the volume of hydrogen given off, when an excess of dilute hydrochloric acid is added to powdered metal. The volume of gas is measured at room temperature and pressure.

The experiment is carried out three times, using the same mass of powder each time but with
* different powders 
* Pure magnesium
* Pure zinc 
* A mixture of magnesium and zinc
Which powder gives the greatest volume of hydrogen and which the least volume ?
The correct option is