A
① the habit-formation theory
② the hypothesis of linguistic universals
③ the acculturation theory
④ the discourse theory
⑤ the monitor theory
B
a. The theory originated in

A
① the habit-formation theory
② the hypothesis of linguistic universals
③ the acculturation theory
④ the discourse theory
⑤ the monitor theory
B
a. The theory originated in the late 1970s and was put forward by J. Schumann and R. Anderson.
b. The theory comes from the behaviourist psychology and was very popular in the 1950s and 60s.
c. The theory was established by E. Hatch in the late 1970s.
d. The theory was put forward by Stephen Krashen in the late 1970s.
e. The theory originates from the study of linguistic universals in natural languages.

①b
②e
③a
④c
⑤d