Give a suitable laboratory preparation method for diborane.

• A
  Reaction of $BF_{3}$ with $LiAlH_{4}$ in diethyl ether.
• B
  Reaction of $NaBH_{4}$ with $I_{2}$ in diglyme.
• C
  Thermal decomposition of $B_{2}H_{6}$.
• D
  Reaction of $BCl_{3}$ with $H_{2}$.