The answers are; B, C & E.
An ecosystem defines all the organism and their interaction with their environment (inducing abiotic factors such as energy from the sun and water). Biomes (which can be defined as a part of the environment that more or less share the same environmental conditions) make up an ecosystem.
Electron;Neutron is the correct answer.
Rust is a chemical change. Chemical changes are when the substances that make up an object change into other chemicals. For example, rust. What happens is metal and oxygen/water react and create rust. Hope this helps :)
3 kilometers, it is just 5/60 or 1/12 multiplied by 36.
We can solve the problem by using the law of conservation of energy.
Using the ground as reference point, the mechanical energy of the brick when it is at 5 m from the ground is just potential energy (because the brick is initially at rest, so it doesn't have kinetic energy):

when the brick is at h'=3 m from the ground, its mechanical energy is now sum of kinetic energy and potential energy:

where v is the velocity of the brick. Since E is conserved, it must be equal to the initial energy (98.1 J), so we can solve this equation to find v: