The Graph of the Derivative $f ^ { \prime } ( x )$

Multiple Choice

The graph of the derivative $f ^ { \prime } ( x )$ of a continuous function $\mathrm { f }$ is shown. On what intervals is $f$ decreasing?

A) $( 1,3 ) \cup ( 4,6 )$
B) $( - 1,1 )$
C) $( 8,9 )$
D) $( 2,6 )$
E) None of these