Answer: Usually age unless its level of fitness but that's kind of vague
Explanation:
So I would say age in moderation because if you have like a 20 year old and a 17 year old doing exercise I don't think there will be a big heat exertion illness getting them down but if your health teachers annoying and is talking about a 18 year old exercising with an 87 year old than its definitely level of fitness
Modern firearms use the same principles as muzzleloading firearms. The ignition and burning of gunpowder create pressure. This pressure propels projectile(s) down the bore and out of the muzzle. The first modern firearms used black powder. Since about 1890, modern firearms are designed to use smokeless gunpowder. Smokeless gunpowder creates greater pressures and should not be used in firearms designed for black powder. Watch what happens when the trigger is squeezed on this bolt action rifle.
The double bubble sign on ultrasound is a sign for duodenal atresia which is associated with Down Syndrome.