Answer:
B. 5 Ω
Explanation:
Resistors in series you can add. Resistors in parallel you should add reciprocal. So in the picture you have 3 "parts" in series:
- a lone 1Ω: 1
- two 4Ω in parallel: 1/(1/4 + 1/4) = 2
- 3Ω and 6Ω in parallel 1/(1/3 + 1/6) = 2
1 + 2 + 2 = 5
