Question

1. to observe the effects of how different metals react, the students should compare...

Explanation:

To observe the effects of different metals reacting, the students should compare beakers where only the metal changes while the acid (type and concentration) remains the same. In options A and B, the acid is dilute sulfuric acid (same type and concentration), with metal changing from iron (A) to copper (B). In options E and F, the acid is dilute hydrochloric acid (same type and concentration), with metal changing from iron (E) to copper (F). This setup isolates the variable of the metal, allowing a valid comparison of how different metals react.

Answer:

A. A and B or E and F