I would think it is a heterogeneous mixture since it can't be an element since there are more than one type of atom, it can't be a compound since the leaves are not bonded together, and it can not be a homogeneous mixture since the leaves don't all blended together (the pile is not uniform) and you can distinguish all the different parts of the mixture. It can be considered a heterogeneous mixture since the leaves are mixed together (along with other things like dirt) in a non-uniform way so that you can point out the parts of the mixture and it does not look like one thing.
I hope this helps. Let me know in the comments if anything is unclear.
Answer:
n = 12.18 moles
Explanation:
Given that,
The volume of a canister, V = 1 L
The temperature of the canister, T = 100 K
Pressure, P = 100 atm
We need to find the number of moles of gas. Let there are n number of moles. We know that,
PV = nRT
Where
R is gas constant, R = 0.0821 L*atm/mol*K

Hence, there are 12.18 moles of gas.
I believe it is either A or B
Good grief, this stuff got caught in a black hole somewhere. It is terribly dense.
1 mL = 1 cc under normal conditions.
d = mass / volume
m = 20 kg
v = 5 mL
d = 20kg / 5 mL
d = 4 kg / mL
d = 4 kg / cc
A <<<<answer