1. Write C for countable and U for uncountable nouns.

Here's how to classify those nouns:

• 1. Biscuit - C (You can have one biscuit or many biscuits)
• 2. Salt - U (Salt is a substance, you can't count individual grains easily)
• 3. Burger - C (You can have one burger or two burgers)
• 4. Juice - U (Juice is a liquid, you usually measure it or drink it, not count individual units)
• 5. Melon - C (You can have one melon or several melons)
• 6. Onion - C (You can have one onion or three onions)
• 7. Bread - U (Bread is usually considered a mass noun, though you can talk about 'loaves of bread' or 'slices of bread')
• 8. Potato - C (You can have one potato or many potatoes)
• 9. Cereal - U (Cereal is a type of food, like 'rice' or 'pasta'. You can have 'a bowl of cereal' or 'many cereals' if referring to different types, but generally it's uncountable)
• 10. Jam - U (Jam is a spread, a type of food. You usually have 'a jar of jam' or 'some jam')