Extent of back bonding, reduces down the group leading to more Lewis acidic strength (2p−2p)BF3>(2p−3p)BCl3>(2p−4p)BBr3>(2p−5p)BI3 (extent of back bonding) BF3<BCl3<BBr3<BI3 (lewis acidic nature) So, the correct option is (B).
P block elements are those in which the last electron enters any of the three p-orbitals of their respective shells. Since a p-subshell has three degenerate p-orbitals each of which can accommodate two electrons, therefore in all there are six groups of p-block elements.
P block elements are shiny and usually a good conductor of electricity and heat as they have a tendency to lose an electron. You will find some amazing properties of elements in a P-block element like gallium. It’s a metal that can melt in the palm of your hand. Silicon is also one of the most important metalloids of the p-block group as it is an important component of glass.