Answer:
A) gradual; knowledge
Step-by-step explanation:
Gradual building of knowledge over one another is fundamental way in which science is developed.
- Science follows a systematic approach to study an observation.
- Each step of the scientific method is to build on existing and known idea about a particular phenomenon.
- An observation is made, questions asked, hypothesis formulated and experiments are designed to know how valid they are.
- Subsequent researches also builds on this flow of investigating a phenomenon.