The answer is blood type bc you won’t know their blood type by just observing them
Xylem Phloem are the vascular tissues that transport the food, minerals and water within the plant. Xylem transport the water and minerals while Phloem transport food and nutrients. The movements in Xylem is unidirectional from roots to aerial parts while the movements in Phloem are bidirectional.
The Griffith's experiment, the Avery-MacLeod-McCarty experiment, and the Hershey–Chase experiments were the set of experiments that established DNA as the key hereditary molecule. The Avery-MacLeod-McCarty experiment was an extension to the Griffith's experiment. The heat killed virulent S strain cells of the Griffith's experiment were lysed to form a supernatant containing a mix of RNA, DNA, proteins and lipids from the cell. The supernatent was equally divided into 3 parts after the removal of the lipids. The 3 parts were respectively treated with an RNAase to degrade the RNA, DNAase to degrade the DNA and proteinase to degrade the proteins. The treated supernatant was then added into the culture containing the non-virulent R cells. In case of the supernatant treated with the DNAse, no transformation of R cells into S cells occurred. The transformation of R cells to S cells occurred in the proteinase and the RNAse cases. This indicated that DNA was the hereditary molecule and not protein or RNA.

The three observations that could help an individual in distinguising whether the organism is a fish or not is that it should live under water as fish can't survive without water, another thing is that it should laid eggs when it comes to giving birth because when it does not lay eggs but produces a living organism normally without an egg, it is considered to be a mammal and lastly, the appearance it possess such as having gils or fins.