The correct option is
B Decreases
Considering the case when switch is open.
![](https://search-static.byjusweb.com/question-images/byjus/infinitestudent-images/ckeditor_assets/pictures/621632/original_New_Bitmap_Image.bmp)
Since wire AC has zero resistance, therefore A and C will be having same potential say
x. Simillarly B and D will be at same potential say
y.
Then equivalent circuit can be drawn as shown below.
![](https://search-static.byjusweb.com/question-images/byjus/infinitestudent-images/ckeditor_assets/pictures/621662/original_New_Bitmap_Image.bmp)
Since all the resistance are equal, current will be divided equally among them. Therefore if current
I is flowing through circuit, then current
I/3 will be flowing through each resistor. Hence current through resistor A when switch is open is
I/3.
Considering the case when switch is closed.
![](https://search-static.byjusweb.com/question-images/byjus/infinitestudent-images/ckeditor_assets/pictures/621652/original_New_Bitmap_Image.bmp)
The equivalent circuit for the above can be drawn as shown below.
![](https://search-static.byjusweb.com/question-images/byjus/infinitestudent-images/ckeditor_assets/pictures/621654/original_New_Bitmap_Image.bmp)
Since all the resistance are equal, current will be divided equally among them. Therefore if current
I is flowing through circuit, then current
I/4 will be flowing through each resistor. Hence current through resistor A when switch is closed is
I/4.
Since the current decreases from
I/3 to
I/4, therefore option B is correct.