test series

Question

Consider R and S be relational schemes such that R={a,b,c} and
S={c}. Now consider the following queries on the database:
I. π_(R-S) (r)-π_(R-S) (π_(R-S) (r)×s-π_(R-S,S) (r) )
II.{t│t∈π_(R-S) (r)∧∀u∈r(∃v∈s(u=v[s]∧t=v[R-S] ) ) }
III.{t│t∈π_(R-S) (r)∧∀v∈r(∃u∈s(u=v[s]∧t=v[R-S] ) ) }
IV.SELECT R.a,R.b FROM R,S WHERE R.c=S.c
Which of the above queries are equivalent?

1. I and II
2.  I and III
3.  II and IV
4. III and IV
    

Comments

Is it option 4?

III and IV