One of the most important parts of doing will in your investigation is choose your topic. You want to remember the KISS motto
K; Keep
I: It
S: Simple
S: Stupid
Your text has several ideas listed on pages 256-257
Topic selection phase
The selection of a suitable topic for investigation may begin with an idea or observation or question about an object, event or phenomenon. Students may have already developed a question as an extension of earlier completed work, or may be curious about a practical problem, or a particular technological development.