C. hydrogen accreted onto a white dwarf from a close companion rapidly fuses to helium, releasing a large amount of energy.
The accreted material, composed mainly of hydrogen, is compacted on the surface of the white dwarf due to the intense gravitational force on that place. As material accumulates, The white dwarf becomes increasingly hot, until it reaches the critical temperature for ignition of nuclear fusion.
Both don’t have units beacuse they are ratios
The object's speed will not change.
In fact, after the astronaut throws the object, no additional forces will act on it (since the object is in free space). According to Newton's second law:

where the first term is the resultant of the forces acting on the body, m is the mass of the object and a its acceleration, we see that if no forces act on the object, then the acceleration is zero. Therefore, the acceleration of the object is zero, and its velocity remains constant.
Answer:
An electric bell is placed inside a transparent glass jar. The bell can be turned on and off using a switch on the outside of the jar. A vacuum is created inside the jar by sucking out the air. Then the bell is rung using the switch. What will we see and hear?
A.
We’ll see the bell move, but we won’t hear it ring.
B.
We won’t see the bell move, but we’ll hear it ring.
C.
We’ll see the bell move and hear it ring.
D.
We won’t see the bell move or hear it ring.
E.
We’ll see the sound waves exit the vacuum pump.
Explanation:
so, the answer to the question is
A.
We'll see the bell move, but we won’t hear it ring.