Which of these events is pre-columbian? a. the native american population reached 50 million people. b. the spanish introduced horses to native americans. c. the spanish shared tools with native americans. d. the native american population decreased to 8 million people.

The correct answer is A) The Native American population reached 50 million people. 

The event that is pre-Columbian is "Native American population reached 50 million people."

When it is said that the event was pre. Columbian means that it happened before the arrival of Cristopher Columbus to the Americas. According to historians, Columbus arrived in the Americas on October 12, 1492.

So before Columbus arrived, the Native American population reached 50 million people. But after this, the Spanish introduced horses to Native Americans, shared tools with them and the Native American population decreased to 8 million people due to the many that Europeans brought to the Americas, practically unknown to the Native Americans such as influenza, smallpox, malaria, chickenpox, measles, cholera, and typhus, among many others. These diseases killed millions of native American Indians.

a is correct

hope this let me know if it is right

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plan to start slowly and boost your activity level gradually unless you are already exercising frequently and vigorously.

be aware that training too hard or too often can cause overuse injuries like stress fractures, stiff or sore joints and muscles, and inflamed tendons and ligaments. sports prompting repetitive wear and tear on certain parts of your body — such as swimming (shoulders), jogging (knees, ankles, and feet), tennis (elbows) — are often overuse culprits, too. a mix of different kinds of activities and sufficient rest is safer.

listen to your body. hold off on exercise when you're sick or feeling very fatigued. cut back if you cannot finish an exercise session, feel faint after exercise or fatigued during the day, or suffer persistent aches and pains in joints after exercising.

if you stop exercising for a while, drop back to a lower level of exercise initially. if you're doing strength training, for example, lift lighter weights or do fewer reps or sets.

for most people, simply drinking plenty of water is sufficient. but if you're working out especially hard or doing a marathon or triathlon, choose drinks that replace fluids plus essential electrolytes.

choose clothes and shoes designed for your type of exercise. replace shoes every six months as cushioning wears out.

for strength training, good form is essential. initially use no weight, or very light weights, when learning the exercises. never sacrifice good form by hurrying to finish reps or sets, or struggling to lift heavier weights.

exercising vigorously in hot, humid conditions can lead to serious overheating and dehydration. slow your pace when the temperature rises above 70°f. on days when the thermometer is expected to reach 80°f, exercise during cooler morning or evening hours or at an air-conditioned gym. watch for signs of overheating, such as headache, dizziness, nausea, faintness, cramps, or palpitations.

dress properly for cold-weather workouts to avoid hypothermia. depending on the temperature, wear layers you can peel off as you warm up. don't forget gloves.