As a general rule to follow, what does it mean when you see a red marking on the safety mechanism of your firearm?

For the difference command to work, what needs to happen?

Many colleges review students’ scores on the _ or _ before deciding whether to offer them admission.

Above is a picture of one of the most famous discoveries ever to be found in china. answer the following questions: - what does the picture show? - when and where was it discover? - who discovered it and what was he doing when he/she discovered it?