বিজ্ঞান মডেল টেস্ট ২

Explanation
The density of water at 4 degrees Celsius is 1 gram per cubic centimeter.

Explanation
For aquatic organisms like water animals, a minimum of 5 milligrams of oxygen is required in 1 liter of water for survival.

Explanation
Graphite is used in pencils because of its unique properties. It is a form of carbon that has a layered structure, with weak bonds between the layers. This allows the layers to easily slide over each other, leaving a mark on the paper when pressure is applied. Graphite is also soft and brittle, making it ideal for use in pencils. Magnetite, mica, and quartzite are not commonly used in pencils.