若a=3,b=4,c=5,d=6,则条件表达式a<b?a:c<d?c:d的值是（  ）。

A、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">4&nbsp;&nbsp; </span>

B、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px; TEXT-DECORATION: none">3&nbsp; </span>

C、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">2&nbsp;&nbsp; </span>

D、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">1</span>