Four of the stages in the life cycle of a star, up to the point when it becomes a red giant, are shown. W The inward pull of gravitational attraction is exactly matched by an outward force from its centre. X Gravitational collapse inside the star causes the temperature to rise. Y The star increases in size. Z Most of the hydrogen has changed into helium. What is the correct sequence of these stages, beginning with the earliest?
- AW X Y Z
- BW X Z Y
- CX W Y Z
- DX W Z Y