_____ were used to construct buildings.
 a. Mud and hay
 
 b. Mortar and cement
 
 c. Sun-dried bricks
 
 d. Baked bricks
Answer:
The correct option is (a).
Explanation:
- 
  
   The use o
  
  
   f baked bricks allowed the Indus Valley people to construct buildings that were stronger and more durable
  
  
   than those made of mud bricks.
   
 - The baked bricks were also uniform in size and shape, making them easier to stack and arrange in a planned manner.