Division Bryophyta is also known as the amphibian plant group. They are evolved than Thallophyta members. They are found in wet, moist places, near the water body. They need water for their reproduction and fertilization.

The correct answer is option 'C' - their reproductive phase requires water.

Bryophytes, which include mosses, liverworts, and hornworts, are known as the amphibians of the plant kingdom because their reproductive phase requires water. Let's delve into the details to understand why this is the case.

Water is essential for the reproduction of bryophytes due to their unique life cycle and reproductive structures. Bryophytes are non-vascular plants, meaning they lack specialized tissues for conducting water and nutrients throughout their bodies. This limitation makes them highly dependent on water for various biological processes, including reproduction.

Here is an explanation of why each option is not the correct answer:

a) Differentiated body: Bryophytes do have a differentiated body compared to algae, but this characteristic alone does not make them amphibians of the plant kingdom.

b) Multicellular and jacketed sex organs: While it is true that bryophytes have multicellular and jacketed sex organs, this characteristic is not unique to them and does not make them amphibians of the plant kingdom.

c) Reproductive phase requiring water: This is the correct answer. The reproductive phase of bryophytes, known as the gametophyte stage, requires water for the sperm to swim to the egg. Without water, the sperm would not be able to reach the egg for fertilization to occur.

d) All of these: This option is the correct answer, as all of the given options are true for bryophytes. However, the key characteristic that sets them apart as amphibians of the plant kingdom is their dependence on water for reproduction.

In summary, bryophytes are called amphibians of the plant kingdom because their reproductive phase requires water. This necessity is due to their lack of vascular tissues and their reliance on water for the sperm to reach the egg during fertilization.