a.      6

b.      5

c.      1

d.      3

e.      4

f.       2

a.      If you know how to use a computer, you can register for the workshop

b.      If you don’t know how to use a computer, you must register for the computer lab first

c.      Could you do it now?

d.      Your parents must fill in and sign this application form

e.      You can give me these papers today or tomorrow

a.      Expressing obligation

b.      Expressing possibility

c.      Expressing lack of obligation

d.      Expressing impossibility

e.      Expressing prohibition

a. if

b. because

c. then