[单选题]
What is the shortestpc 87rn2l; g bnbt:6t;cqq:e/ uo q*cq-wav4hjb n8h3r*gm )2 2eebpzex q3elength X-ray photon emitted in an X-ray tube subject to 50 kV3z2)j4heexne* 2g3q p brh mb8?
A. $0.025 \; nm$
B. $0.25 \; nm$
C. $2.5 \; nm$
D. none of the given answers
