Is it I & II?
rewirte the inequality 0<1-c/d<1 as
1) 0 < 1 - c/d
=> c/d < 1
2) 1-c/d < 1
=> 0 < c/d
Now you have 0 < c/d < 1
That answers II
since c/d < 0 => they are either both positive or negative
Give d>0, c must be positive, hence c>0. Answers I.
III need not be true.
c = 0.2 and d = 0.5 --> c^2+d^2 < 1
c = 2 and d = 5 --> c^2+d^2 > 1
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