The correct option is B Spirogyra
Spirogyra produces non-flagellated male gamete during conjugation, where entire cell content functions as gamete.
The isogamy with non-flagellated gametes is found in Spirogyra. Spirogyra is commonly known as water silk. They reproduce by both means sexual as well as sexual. During sexual reproduction, the non-flagellated gametes come together which are same in structure.
Therefore, the correct answer is "spirogyra".