What is caffeine?

Caffeine can increase anxiety levels.

The most commonly used substances excludes. ( ) A: caffeine B: alcohol C: nicotine D: tea

Athletes should avoid having drinks containing caffeine, for they are hundred-percent harmful to the athletes’ sports performance.

The specific purpose of the “caffeine sample” is to _____. A: inform the audience of the facts about caffeine and its effects on our body B: inform the audience of the events leading to Ophelia’s death C: persuade the audience to applaud the performance D: persuade Romeo to abandon his family name

Tea contains（ ）and protects against cancer. A: antioxidants B: caffeine C: theanine D: anti-inflammatory properties

The factors enhancing contractility of muscle are () A: Ca2+ B: caffeine C: adrenaline D: hypoxia E: acidosis

( )is found in both tea and coffee to increase excitability. A: Amino acids B: Caffeine C: Vitamins D: Minerals

Which of the following aids in the absorption of calcium? A: Caffeine B: Low stomach acidity C: Iron D: Vitamin D

If you have trouble sleeping at night, ______. A: limit caffeine intake B: limit alcohol intake C: take naps D: limit smoking