According to the given options, the correct answer is option D, which includes the plants Ficus and Gelidium. Let's understand why these plants are considered oogamous and non-motile in terms of their male gametes.

Oogamy and Non-Motile Male Gametes:
Oogamy is a type of sexual reproduction in which the female gamete or egg is large and non-motile, while the male gamete or sperm is small and motile. This type of reproduction is commonly observed in plants and algae.

Ficus:
- Ficus is a genus of plants that includes fig trees. These plants exhibit oogamy in their reproductive process.
- The female gamete, also known as the egg or ovum, is produced in the ovary of the fig flower. The ovum is relatively large and non-motile.
- On the other hand, the male gamete, also known as the sperm or pollen, is produced in the anther of the fig flower. The pollen grains are small and non-motile.

Gelidium:
- Gelidium is a type of red algae that also shows oogamous reproduction.
- In Gelidium, the female gamete, called the carpogonium, is a large and non-motile structure.
- The male gamete, called the spermatium, is small and non-motile. It is released from the male reproductive structure and fuses with the carpogonium to facilitate fertilization.

In both Ficus and Gelidium, the male gametes are non-motile. This means that they cannot move on their own to reach the female gametes. Instead, they rely on external factors like wind, water, or other organisms for transfer and fertilization.

In conclusion, Ficus and Gelidium are examples of plants that exhibit oogamous reproduction, where the male gametes are non-motile.