The equivalent resistance between the terminal A and B is:

Correct option is B

​$$\text{• The circuit consists of two parallel branches, and each branch has two } 50\Omega \text{ resistors in series:}$$​$$R_{\text{series}} = 100\Omega + 100\Omega = 200\Omega$$

$$\text{• The two series combinations are connected in parallel:}$$

$$\frac{1}{R_{\text{eq}}} = \frac{1}{200} + \frac{1}{50}$$

$$R_{\text{eq}} = 40\Omega$$​​​​​