[单选题]
Starting from city A, a car i q (w5:l 62uqv2ira0 acb :horxf(kt2s74tdrdrive:;j binql7bf k0uo, 6is 250 miles east to city B, then 300 miles north to city C, and fi6n jbqi7io;l fk0 :b,unally 700 miles west to city D. What is the distance between city A and city D?
A. $300 \; mi$
B. $400 \; mi$
C. $500 \; mi$
D. $600 \; mi$