The electric field surrounding two point charges: a) is the vector sum of the electric field that would be caused by each charge separately.
b) zero at all points along the line connecting the two charges.
c) cannot be determined.
d) cannot be zero anywhere.
e) none of the above.

a) is the vector sum of the electric field that would be caused by each charge separately.

Explanation: In order to explain this problem we have to know the electric field can be calculated by using the superposition principle so in this case this the right answer.

All the other are false, b) never can be the field zero along a line that connect the charges because it depend on teh sign of the charge and the distance between them. c) always the electric field can be determined for charged points. d) It is possible to find a zero electric field in any point if the points charges have different sign.  

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.