"Voltage" is the "pressure" that makes electrons want to leave where they are
and head in some direction, if there's conducting material in that direction.
"Current" is the rate at which they all migrate in that direction.
Answer:

Explanation:
M = Mass of each star
T = Time period = 15.5 days
v = Orbital velocity = 230 km/s
G = Gravitational constant = 
Radius of orbit is given by

We have the relation

The mass of each star is 
B: new technology allowed microscopes to make it easier to view things that had never been seen before, such as cells
C: new technology allowed microscopes to produce still images on a computer screen
D: new technology allowed to create realistic three-dimensional pictures
E: new technology allowed microscopes to map the atom on the surface of an object