Final answer:
A slope is considered shallow when it is flat or has a small angle of inclination. The shallow ends of the island can be represented by a horizontal line at some negative value.
Step-by-step explanation:
Slope is a measure of how steep or shallow a line is. In general, a slope is considered shallow when it is flat or has a small angle of inclination. So, the correct answer to determine if a slope is shallow is b) The slope is shallow when it's flat.
Regarding the ends of the island, the question does not provide enough information to determine which directions the shallow ends are. However, based on the given options, a shallow end would be represented by a horizontal line at some negative value, so the correct answer would be c) It is a horizontal line at some negative value.