"Sacred" means （）.

单项选择题The author compares cells with water balloons in order to （）.

A．make you think of summer
B．help you visualize the cells
C．show how rubber is elastic
D．show how many shapes cells can have

单项选择题To give us an idea of how large the rafflesia is, the author uses （）.

A．the size of an elephant for comparison
B．measurements
C．comparisons to other flowers
D．detailed descriptions of the flower’s stem