**Explanation:**

The name "Protist" was proposed by C. Cuvier, and the group "Protista" was raised by Haeckel to include a diverse group of organisms that do not fit into the other traditional classifications of plants, animals, or fungi. The correct answer to the question is option 'D', which states that protists include heterotrophs.

**Unicellular Eukaryotes:**
- Protists are primarily composed of unicellular eukaryotes, meaning they have a true nucleus and other membrane-bound organelles.
- Examples of unicellular eukaryotic protists include amoebas, paramecium, and euglena.

**Unicellular Prokaryotes:**
- Unicellular prokaryotes, such as bacteria, are not included in the group of protists.
- Prokaryotes lack a true nucleus and other membrane-bound organelles.

**Living Beings That Do Not Produce Tissues:**
- While it is true that protists do not produce tissues like plants and animals, this statement does not encompass the full range of organisms included in the protist group.
- Protists can exhibit a wide range of cellular organization, from unicellular to multicellular forms.
- Some protists, such as algae, can form simple tissues, while others remain unicellular.

**Heterotrophs:**
- The correct answer to the question is option 'D', which states that protists include heterotrophs.
- Heterotrophs are organisms that obtain their energy by consuming other organisms or organic matter.
- Many protists are heterotrophs, feeding on bacteria, other protists, or organic debris.
- However, it is important to note that not all protists are heterotrophs. Some protists are autotrophs, capable of producing their own food through photosynthesis.

In conclusion, the name "Protist" was proposed to encompass a diverse group of organisms that do not fit into traditional classifications. Protists primarily include unicellular eukaryotes but not unicellular prokaryotes. While protists do not produce tissues like plants and animals, this statement does not fully define the group. The correct answer to the question is option 'D', as protists include heterotrophs, although some protists are also autotrophs.

What the hell this app is ....its answer should be (a). this app is misguiding