(a) How does the study of fossils help to understand evolution.

Explanation

**Step-by-Step Solution:**

1. **Introduction to Fossils and Evolution:**
Fossils are the preserved remains or traces of organisms from the past. The study of fossils, known as paleontology, provides crucial insights into the history of life on Earth and the process of evolution.

2. **Fossils as Historical Documents:**
Fossils act like written documents that record the existence of different species at various geological periods. They provide evidence of what organisms looked like and how they lived, which helps scientists understand the timeline of evolution.

...