[单选题]
Which of the following characteristics of transition metals resp2g47qxiiynnb c:i+ n 5 7h;e90rxszf o yy//1vo;-eah -cgneults in high electryeoeo g cy--1av /h/;nical conductivity?
A. Large atomic radius
B. Strong ionic bonds
C. High relative atomic mass
D. Delocalized electrons in unfilled d-orbitals
