Answer: B. Housing is expensive and time-consuming to build.
Step-by-step explanation:
Supply of housing cannot keep up with increases in demand simply because housing is not an easy good to supply. Building a house takes time and is quite expensive because land needs to be bought, materials as well and then there is the labor to pay for as well.
In the face of this, the people who want houses often find that they cannot get houses fast enough because the suppliers are sourcing funds and rightfully taking time to make houses available.