Hi,
From(1): m and n are interchangeable. So we cannot say m/n is less than 1
example: if m = -1/2, n = -1/4, m/n = 2(greater than 1)
if m = -1/4, n = -1/2, m/n = 1/2(less than 1)
Not sufficient

From(2): m-n>n
So, m > 2n
As n is negative, m/n < 2
We can't say whether m/n is less than 1 or not
Not sufficient

Both(1)&(2): mn<1 and m>2n
if m = -1/2, n = -1/3, m/n = 3/2(>1)
if m = -1/6, n = -1/3, m/n = 1/2(<1)
Not sufficient

Hence, E