Which of the following is always an important part of an experiment?

1. making a working model

2. observing things in nature

3. making drawings of things observed

4. identifying and controlling variables

The most important part of an experiment would be; identifying and controlling variables.

In order to set up an experiment, you need to test the specimen (s) with and without a curtain variable. That is what makes an experiment a test.

identify and controlling variables

Explanation:

lack of awareness of control variables can lead to faulty result or what are called "confounding variables" additionally, noting control variables makes it easier to reproduce and experiment and establish the relationship between the independent and the dependent variable