[单选题]
07.04: A particle moves gm hn 7*i;e8ujon thtgjaj h7d-g,)c8r* 7wc 3pmjl e x-axis. When the acceleration is positive and increasp,8t7ljw mc )*7 -jrggjacdh3ing
A. its velocity must be positive.
B. its velocity must be negative.
C. it must be slowing down.
D. it must be speeding up.
E. none of the above must be true.
