1.abbr. pound; unit of weight in ancient Rome equaling approximately 12 ounces

　　(a) attn.

　　(b) lb

　　(c) pd.

　　(d) AOL

　　2.abbr. manpower; personnel; human work force; human labor; staff

　　(a) corp.

　　(b) H.R.

　　(c) R&D

　　(d) HTML

　　3.abbr. directed to a particular person (generally used when addressing a letter or message) or issue

　　(a) attn.

　　(b) PTO

　　(c) C.T.O.

　　(d) C.C.

　　4.abbr. between noon and midnight; in the afternoon; after the hour of 12:00 noon

　　(a) p.m.

　　(b) C.C.

　　(c) C.O.O.

　　(d) Ltd.

　　5.abbr. secondary email address; copy of a document, message, or email that is sent to a third party

　　(a) G.D.P.

　　(b) PR

　　(c) i.e.

　　(d) C.C.

　　答案：bbaad