Round 237.95 to four significant figures

Iknow the answer is a but i don't know why

Turbo the snail moves across the ground at a pace of 12 feet per day. if the garden is 48 feet away, how many days will it take for the snail to get there?

Which change in temperature is the smallest? a change of 1 thomson degree a change of 1 kelvin degree a change of 1 fahrenheit degree a change of 1 celsius degree