Which part of an amino acid is the only one that varies and is what defines the properties

Why do mountaineers become breathless as they reach high altitudes

The first supersonic flight was 1947. it was just above the speed of sound. which altitude would you expect captain yeager to have used for his flight? a) sea level b) 1000m c) 13,700m (within altitude used by commercial planes today) d) 85,000m (where meteor showers originate) will mark brainlist

The amount of time it takes for one-half of the original amount of an isotope to decay is known as its question 9 options: correlation half-life period radioactivity