The correct words for the blanks are (i) ecologists, (ii) monogamous, and (iii) biodiversity.

Breakdown of the Blanks
- Blank (i): C. ecologists

The passage describes a "study" involving wildflowers and bumblebees, focusing on their relationship within an ecosystem. A person who studies the relationship between organisms and their environment is an ecologist. This is the most accurate term for the scientists conducting the study.
- Blank (ii): D. monogamous

The sentence says that the relationship is faithful, with each bee species focusing on a "single plant variety until it finishes blooming." The word that describes this type of one-toone relationship is monogamous. This fits the context of bees and flowers being faithful to each other.
- Blank (iii): I. biodiversity

The final part of the sentence explains the "importance of...in the conservation of ecosystems." The example given is that the "removal of a bee species resulted in decreased plant reproduction." This illustrates the importance of having a variety of species in a healthy ecosystem. Biodiversity is the variety of life in the world or in a particular ecosystem, and the study clearly underlines its importance.