Answer:
Option D, Aluminum
Step-by-step explanation:
Valency of boron and hence it requires three electron to complete its outermost shell.
Valency of Aluminum is also three and it can donate three electrons to boron to complete the outermost shell of itself as well as the boron.
Hence, Aluminum and Boron will form 1:1 bond with each other. (Al-B)
Hence, option D is correct