A particle moves along a horizontal line for 0<t<5. Its velocity satisfies f′(t)>0 on (0,2)∪(4,5) and f′(t)<0 on (2,4). Its acceleration satisfies f′′(t)>0 on (1,3) and f′′(t)<0 on the remainder of the interval. On which of the following intervals is the particle speeding up?
a) (1,3)
b) (0,2)∪(4,5)
c) (1,2)∪(3,4)
d) (1,2)