In the natural water cycle, which of the following processes together are mainly responsible for causing rain?

Introduction / Context:
Rainfall is a key part of the water cycle on Earth. Understanding how water moves from the surface to the atmosphere and back again is fundamental in school level geography and science. This question asks you to identify which processes are mainly responsible for the formation of rain, focusing on the transformation of water from liquid to vapour and back to liquid droplets in clouds.

Given Data / Assumptions:

• We are dealing with the natural water cycle that includes processes like evaporation, condensation and precipitation.
• The question is specifically about what causes rain, not about purification methods or artificial treatments.
• Options include filtration, evaporation, condensation and the combination of evaporation and condensation.

Concept / Approach:
In the water cycle, water from oceans, lakes, rivers and soil is heated by the Sun and changes from liquid to vapour in a process called evaporation. This water vapour rises, cools at higher altitudes and then changes back into tiny liquid droplets, which is called condensation. These droplets form clouds. When the droplets grow large and heavy enough, they fall to the ground as rain. Thus, rain formation depends on both evaporation (to supply water vapour) and condensation (to form droplets in clouds). Filtration is a human made process for cleaning water, and using only one of the two natural processes does not describe the full path to rainfall.

Step-by-Step Solution:
Step 1: Recall the sequence of steps in the water cycle: evaporation, condensation, cloud formation and precipitation. Step 2: Understand that evaporation converts surface water into water vapour that rises into the atmosphere. Step 3: Recognise that condensation converts water vapour into tiny droplets, which cluster to form clouds. Step 4: When these droplets combine and grow heavy, they fall as rain, completing the key steps leading to rainfall. Step 5: Compare this understanding with the options given and see that both evaporation and condensation are required. Step 6: Choose Evaporation and Condensation as the most complete and correct description.

Verification / Alternative check:
Diagrams of the water cycle in textbooks always show evaporation from water bodies, followed by rising vapour and condensation into clouds, then precipitation. None of these diagrams include filtration as a natural step. Also, if there were only evaporation without condensation, water would simply stay as vapour, and if there were only condensation without prior evaporation, there would be no new water vapour supply. Therefore both processes are necessary and this matches the combined option.

Why Other Options Are Wrong:
Filtration: This is a physical method used by humans to remove solid impurities from water. It does not directly cause natural rainfall in the atmosphere.
Evaporation: This alone only moves water into the vapour phase. Without condensation, there would be no formation of droplets and thus no rain.
Condensation: While condensation is directly responsible for droplet formation, it cannot occur in isolation without an earlier source of vapour provided by evaporation, so the single word answer is incomplete.

Common Pitfalls:
Some students see the word rain and immediately think of condensation only, because it is the step where water vapour turns into liquid droplets. Others may focus on evaporation only because it is easy to visualise water turning to vapour. The key is to remember that the complete cause of rain in the water cycle involves both evaporation to create vapour and condensation to form droplets. Paying attention to the phrase causing rain in the question encourages you to pick the combined process option.

Final Answer:
Rain in the natural water cycle is mainly caused by the combined processes of Evaporation and Condensation.