Chair, table, and plough are made up of wood.

Explanation:
Wood is the correct answer because traditionally, chairs, tables, and ploughs have been made primarily from wood. Wood is a natural material that has been used for centuries due to its availability, durability, and versatility.

1. Importance of Wood:
- Wood is a renewable resource, as trees can be replanted and harvested sustainably.
- It is a strong and resilient material, capable of withstanding various loads and pressures.
- Wood is easily workable, allowing for intricate designs and shaping.
- It has a natural beauty with unique grain patterns and colors.

2. Chair:
- A chair is a piece of furniture designed for sitting, typically with a backrest and four legs.
- The frame of a chair is commonly made from wood, providing stability and support.
- The seat and backrest may also be made from wood, often with cushions or upholstery for comfort.

3. Table:
- A table is a flat surface supported by legs, used for various purposes such as dining, working, or playing games.
- Tables can be made entirely from wood, with the top and legs constructed using wooden boards or planks.
- Wood is preferred for tables as it is sturdy and can withstand the weight and pressure placed on it.

4. Plough:
- A plough is an agricultural tool used for turning over soil in preparation for planting crops.
- Traditional ploughs consist of a wooden beam or handle with a metal blade called a ploughshare.
- The wooden beam provides stability and control while the metal blade penetrates the soil.

5. Other Materials:
- While it is possible to find chairs, tables, and ploughs made from other materials like plastic, iron, or even paper, these materials are not as commonly used as wood.
- Plastic chairs and tables are lightweight and easily portable, but they lack the durability and natural aesthetics of wood.
- Iron or metal tables may be used in outdoor settings for their weather resistance, but they are less common for indoor furniture.
- Paper is not a suitable material for constructing chairs, tables, or ploughs due to its lack of strength and durability.

In conclusion, chairs, tables, and ploughs are traditionally made from wood due to its availability, strength, workability, and natural beauty.