The correct answer is option 'D': Spermatophyta. Let's understand why.

Gametophyte and Sporophyte
- In the plant life cycle, there are two main stages: gametophyte and sporophyte.
- The gametophyte stage produces gametes (sex cells), which fuse during fertilization to form a zygote.
- The zygote then develops into the sporophyte stage, which produces spores.

Gametophyte and Sporophyte in Different Plant Groups
- Different plant groups show variations in the relationship between the gametophyte and sporophyte stages.
- In bryophytes (option 'A'), such as mosses, the gametophyte is the dominant and independent stage, while the sporophyte is small and dependent on the gametophyte.
- In pteridophytes (option 'B'), such as ferns, the sporophyte is the dominant and independent stage, while the gametophyte is small and dependent on the sporophyte.
- Cryptogams (option 'C') is a general term used for non-flowering plants, including bryophytes, pteridophytes, and other groups.

Gametophyte Embedded in Sporophyte
- The term "embedded" suggests that the gametophyte stage is enclosed or protected within the sporophyte stage.
- This characteristic is seen in the spermatophytes (option 'D'), which are seed-bearing plants.
- In spermatophytes, the sporophyte stage is dominant and well-developed, while the gametophyte stage is reduced and enclosed within specialized structures.
- The gametophyte of spermatophytes is highly reduced and dependent on the sporophyte for nutrition and support.

Examples of Spermatophytes
- Spermatophytes include gymnosperms (naked seed plants) and angiosperms (flowering plants).
- In gymnosperms, such as conifers, the female gametophyte is contained within the ovule, which is part of the sporophyte structure.
- In angiosperms, the female gametophyte, also known as the embryo sac, is protected within the ovary of the flower.

Conclusion
In summary, the correct option is 'D' because spermatophytes (seed-bearing plants) have the gametophyte stage embedded within the sporophyte stage. This relationship is unique to spermatophytes and is not observed in bryophytes, pteridophytes, or other cryptogams.

The sporophyte produces spores (hence the name) by meiosis, a process also known as "reduction division" that reduces the number of chromosomes in each spore mother cell by half. The resulting meiospores develop into a gametophyte. ... The mature gametophyteproduces male or female gametes (or both) by mitosis.