a) Write a letter to your friend inviting him/her to your birthday party. [3] b) Write a short paragraph on the causes of water pollution. [2]

Sender's address & dateKathmandu15th September, 2013

SalutationDear Sita

GreetingI hope this letter finds you in good health and high spirits.

Body

I am writing to invite you to my birthday party, which will be held on **20th September, 2013**, at my home located in **Balkhu, Lalitpur**. The celebration will start at **4:00 PM** and will continue until **8:00 PM**. I would be truly delighted if you could join me on this special occasion.

The party will include a variety of fun activities such as games, music, and delicious food. There will also be a small gathering of my close friends and family members. Your presence would make the day even more memorable for me.

Please let me know by **18th September, 2013**, if you can attend so that I can make the necessary arrangements. If you have any dietary restrictions or preferences, kindly inform me in advance.

Looking forward to celebrating this joyous occasion with you!

Closing & signatureYour loving friendRama

b) Causes of Water Pollution

Water pollution is a serious environmental issue that affects both human health and ecosystems. The primary causes of water pollution can be categorized into natural and human-induced factors.

Natural causes include:

• Erosion: Soil particles and minerals wash into water bodies during heavy rains or floods.
• Volcanic eruptions: Release toxic substances like sulfur and ash into water sources.
• Decaying organic matter: Natural decomposition of plants and animals can deplete oxygen levels in water.

However, human activities are the major contributors to water pollution. Some key human-induced causes are:

• Industrial waste discharge: Factories release harmful chemicals, heavy metals (e.g., lead, mercury), and toxic substances into rivers and lakes.
• Sewage and domestic waste: Improper disposal of household waste, including detergents, oils, and human excreta, contaminates water sources.
• Agricultural runoff: Pesticides, fertilizers, and animal waste from farms wash into water bodies, causing eutrophication (excessive nutrient buildup).
• Oil spills: Accidental or intentional release of petroleum products from ships, refineries, or vehicles pollutes waterways.
• Plastic and solid waste: Improper disposal of plastic bags, bottles, and other non-biodegradable materials clogs waterways and harms aquatic life.
• Mining activities: Release of toxic metals (e.g., arsenic, cadmium) into groundwater and surface water.
• Deforestation: Reduces natural filtration of water, leading to increased sediment and chemical runoff.

Water pollution disrupts aquatic ecosystems, spreads waterborne diseases (e.g., cholera, dysentery), and threatens biodiversity. Addressing these causes requires stricter regulations, public awareness, and sustainable practices to protect our water resources.