How many electrons are in an electrically neutral atom of boron? A) 3 B) 5 C) 6 D) 8

B. five electrons

If you want an explanation, here it is.

The atomic number gives the number of protons. Protons which have a positive charge are balanced by an equal number of electrons in a neutral atom. Boron number 5 has five protons and therefore as a neutral atom also has five electrons.