Which of the following is Autotetraploid?

Answer: Option A

Autotetraploid means a plant that has four sets of chromosomes, all derived from the same species. Imagine if a plant normally has two copies of each chromosome (diploid), an autotetraploid has four copies of each chromosome, all from its own kind.
Let's break down the options:
A) Cynodon dactylon (Bermuda grass): This is known to exist in tetraploid forms. It is an example of a plant with multiple sets of the same genome.
B) Secale cereale (Rye): This is generally diploid, meaning it has two sets of chromosomes.
C) Pisum sativum (Pea): This is also a common diploid plant.
D) Raphanus (Radish): While some variations might exist, it's typically considered diploid.
So, Cynodon dactylon is the best example of an autotetraploid from the options given because it naturally occurs with four sets of chromosomes from its own species.