In Britain, the _________ are all painted red.

In Britain, the _________ are all painted red.
A、letter boxes
B、letters box
C、letters boxes
D、letters‟ boxes
【正确答案】：A
【题目解析】：letter box信箱的复数形式为letter boxes.
句意：在英国，所有的信箱都漆成红色。