It’s the in the west to open a present when someone gives to you.A. custom oneB. habit

问题补充：

It’s the in the west to open a present when someone gives to you.

A. custom, one

B. habit, one

C. bobby, it

D. favour, it

答案：

(答案→)A. custom, one

B. habit, one

C. bobby, it

D. favour, it

解析：custom（国家，民族等的）习惯，风俗；habit自然养成的，不易去掉的个人习惯；bobby警察； favour善行，帮助。one代词，表示承接前面已出现过的同种类可数名词，表示承接同一个东西时用it；根据句意这是西方的习俗，当收到礼物时打开看一下。故选A。