Which of the following factors directly affects the resistance of a conductor?

Correct option is A

Correct option: (a), Length of the conductor

Key points: 

1. ​Length of the conductor: The longer the conductor, the greater its resistance. This is because electrons encounter more collisions as they travel through a longer path.
   
2. Cross-sectional area of the conductor: The larger the cross-sectional area, the lower the resistance. A larger area allows more electrons to flow through at the same time, reducing resistance.
   
3. Material of the conductor: Different materials have different resistivities (resistance to electrical flow). For example, copper has low resistance (high conductivity), while materials like rubber or glass have high resistance.
   
4. Temperature of the conductor:  As temperature increases, the resistance of most conductors increases as well. This is because the atoms in the conductor vibrate more at higher temperatures, causing more collisions for the electrons.