Through (A)____ and (B)____ kingdoms have been a consta under all different systems, the understanding of what group organisms be included under these kingdoms have been changing the (C)____ and (D)_____ of other kingdom have also been understood differently by different scienitits over time.

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Context**: The question is about the classification of living organisms into kingdoms. Historically, organisms have been categorized primarily into two broad groups: plants and animals.

2. **Filling in the Blanks**:
- **(A)**: The first blank refers to the primary groups under which organisms have been classified. The most basic classification system recognizes two kingdoms: plants and animals. Therefore, we fill in (A) with "plants".
- **(B)**: The second blank also refers to the other primary group in the classification system. Since we are discussing the two main groups, we fill in (B) with "animals".
- **(C)**: The third blank refers to the evolving understanding of how organisms are classified into these kingdoms. As more organisms were discovered and studied, the number of recognized kingdoms increased. Therefore, we fill in (C) with "number".
- **(D)**: The fourth blank relates to the criteria or characteristics used to classify these organisms. Over time, scientists have used various characteristics, including cellular structure and function, to classify organisms. Thus, we fill in (D) with "nature".

3. **Final Sentence**: Putting it all together, the completed sentence reads: "Through (A) plants and (B) animals, kingdoms have been a constant under all different systems; the understanding of what group organisms be included under these kingdoms have been changing the (C) number and (D) nature of other kingdoms have also been understood differently by different scientists over time."