Each myofibril has alternating light and dark bands. The light bands are Group of answer choicesI bandsA bandsH zonesZ lines

The light bands in a myofibril are referred to as I bands.

Explanation:

1. I Bands: These are the light bands that appear under a microscope, and they are primarily composed of thin filaments (actin) and are lighter in color due to less density.
2. A Bands: These are the dark bands in myofibrils, containing thick filaments (myosin) along with some overlapping thin filaments.
3. H Zones: This is a lighter zone within the A band, which appears when the muscle is relaxed, indicating a lack of overlap between actin and myosin.
4. Z Lines: These are the boundaries that demarcate the ends of each I band and anchor the thin filaments.

In summary, the correct choice for the light bands in a myofibril is I bands.