Option : (D)
Construction :
Join A to C
Mark the intersection point of AC and MN as O
Now,
M and N are mid points of the non-parallel of a trapezium
Therefore,
MN || AB || DC
So,
MO || BC
And,
M is a mid-point of AD
Therefore,
MO = \(\frac{1}{2}\)BC
Similarly,
NO = \(\frac{1}{2}\)AB
Therefore,
MN = MO + NO
= \(\frac{1}{2}\)(AB + CD)
But,
MN = 14 cm
Hence,
\(\frac{1}{2}\)(AB + CD) = 14 cm
12 + CD = 28
CD = 16 cm