Which statement best describes a situation in which opposite quantities combine to make 0?

a.
a hot air balloon used propane to fly 50 feet higher, then used weights to fly 50 feet lower.

b.
a farmer mowed 5 inches off his grass one week, then it grew 4 inches the next week.

c.
a child grew 1.5 inches taller one year, then 1.5 inches taller the next year.

d.
a scuba diver swam to a location 25 feet below sea level, then she swam 8 feet deeper.