A balloon travels upward at $1.0\ m/s$ for half of the distance of its trip. It moves upward at $2.0\ m/s$ for the other half of the distance of its trip.

The balloon's average speed for the entire trip is

A

$1.5\ m/s$

B

less than $1.5\ m/s$

C

greater than $1.5\ m/s$

D

$0\ m/s$

E

Not enough information is given to answer this question.