Which number has four significant figures?

A. 4000
B. 3.008
C. 86.012
D. 0.0001

a. 4000

This has 4-digits.

in my opinion letter d.

Explanation:

Sana pi tama

i cant see the choices man

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.