Which of the following is the electron deficient molecule?

$\mathrm{B}_2 \mathrm{H}_6$ is electron deficient molecule because boron atom has three half filled orbitals in excited state. The structure of $\mathrm{B}_2 \mathrm{H}_6$ is represented as follows: In it two electrons of a $\mathrm{B}-\mathrm{H}$ bond are involved in formation of three centre bond, these bonds are represented as dotted lines.