There are really only two choices there ... hot air rising is one PART of a convection current, and convection current happens because of physical properties.
Fuel can burn in a furnace because of its chemical properties. <em>(B)</em>
Answer:
The group speed is 
.
Explanation:
Given that,
Phase speed 
Where, T = period of the wave
g =acceleration due to gravity
We need to calculate the group speed
Using formula of phase speed
Put the value of 
....(I)
We need to calculate the group speed
Using formula of group speed
On differentiating
Put the value of k from equation (I)
Hence, The group speed is .
Answer:
The jp2003parker guy is extremely wrong
So he says that the size wont matter and a physical change should occur, but how would the size change without having a physical change occur.
Explanation:
As the astronaut moved away from the Earth, the astronaut would experience less gravitational force from the Earth, and the Earth would experience less of a pull from the astronaut (what little pull the astronaut actually produces.) As the astronaut approached the moon, the gravitational pull between them would increase.
Answer:
c. Beryllium
Explanation:
oxygen carries 2-
and Beryllium only element that is 2+
