Which of the following is true about wood ?

Any substance that has free electrons that are available to carry charge from one point to another is called a  good conductor.

Now, Wood has high numbers of electrons present in it, but these electrons are tightly bound to the nucleus of the atom. And since, there are no free electrons, there is no flow of electricity also.
These properties of wood make it a bad conductor, but it is found to be a good insulator.

Hence option (B) is correct.