The last equation gives you the tension in the string on the right:

1.15 m/s to the left (3 sig. fig.).
<h3>Explanation</h3>
Momentum is conserved between the two balls if they are not in contact with any other object. In other words,

, where
stands for mass and
stands for velocity, which can take negative values.
Let the velocity of objects moving to the right be positive.
,
.
Before the two balls collide:
,
.
After the two balls collide:
needs to be found,
.
Again,
,
.
.
is negative? Don't panic. Recall that velocities to the right is considered positive. Accordingly, negative velocities are directed to the left.
Hence, ball A will be travelling to the left at 1.15 m/s (3 sig. fig. as in the question) after the collision.
I would have to say that 'B' and 'D' are both correct.
Increasing the voltage that you're using to operate a circuit
causes the current in the circuit to increase. But current is
just the number of electrons that are flowing through it. So
right there, you have the increase in the number of charges.
Now, every electron that flows through the circuit gives up
some energy on the way. So if there are more electrons
making the trip, then more energy has been put into the circuit.
Jessica, I absolutely love your printing.
I wish I could print so clearly.