SSC CPO Tier 1 Exam 03 Oct 2023 Shift 2

Three Statements are given followed by Three conclusions numbered I, II and III. Assuming the statements to be true, even if they seem to be at variance with commonly known facts, decide which of the conclusions logically follow(s) from the statements.
Statements:
All valleys are mountains.
No sea is a mountain.
Some plains are seas.
Conclusions:
I. Some valleys are plains.
II. No plain is a mountain.
III. No sea is a valley.