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Stage 1
Answer 4 questions correctly in a row.

This passage describes shell shape in pond snails.

a narrow shell (left) and a round shell (right)

A pond snail's shell may be narrow or round. Each shape is better at protecting a snail against a different kind of predator.
A narrow shell provides better protection against crayfish, which attack a snail at the opening of its shell. Narrow shells have smaller openings, so they are harder for crayfish to attack.
A round shell provides better protection against carp, which crush shells with their teeth. Round shells are harder for carp to crush.

The table below describes a possible population of pond snails at the start of a period of time and at the end of that period. The table shows shell shape in the population at each point in time.

Complete the table.