Answer:
1. <--> A.
2. <--> C.
3. <--> D
4. <--> B.
explanation: i know my science!
Answer:
The momentum would be doubled
Explanation:
The magnitude of the momentum of the freight train is given by:

where
m is the mass of the train
v is its speed
In this problem, we have that the speed of the train is unchanged, while the mass of the train is doubled:

therefore, the new momentum is

so, the momentum has also doubled.
Answer:
I'm pretty sure its B and C
Explanation:
B bc the weight is gravitational pull x mass so when the object has same mass the weight is smaller on moon
C bc mass is the same - you can't change it
Lower. Water expands on lower temperatures, meaning less molecules in 1 m3, thus making it less dense