Choose the sentence with correct comma usage. A- When Fredric Chopin was only six his talent as a pianist was obvious and he was
already composing original melodies.

B- When Fredric Chopin was only six his talent as a pianist was obvious, and he was
already composing original melodies.

C- When Fredric Chopin was only six, his talent as a pianist was obvious and he was
already composing original melodies.

D- When Fredric Chopin was only six, his talent as a pianist was obvious, and he
was already composing original melodies.

. a function is a relation in which each input has only one output. in the relation , y is a function of x, because for each input x (1, 2, 3, or 0), there is only one output y. x is not a function of y, because the input y = 3 has multiple outputs: x = 1 and x = 2.

laughter improves people's emotional and well-being.   kavita khajuria is a psychiatrist and he has defined laughter as " physical expression of humour and joy that has numorous protective qualities." when you feel under stress or sad because you have argued with a person you love, you need to laugh to feel strong enough to face the problems.

when you have an exam , you probably feel under stress. laughing will you release this tension. humour decreases the hormones that cause stress. k. khajuria   says that the brain releases some chemical components when we laugh. these chemical components are called neurotrophic factors and they are very important. they support the neurons in the brain and encourage the growth of new neurons. as a conclusion, you should laugh a lot before giving your exam. laughing will you with your exam and with your brain.

if you are having difficult times with friends or family members, laughing will also you face these problems. alannagh kelly is an assistant psychologist. she thinks that laughter can   make anger and anxiety vanish in the air. laughter can set a new and exciting atmosphere among people and it can make the bonds bewteen people stronger. so, if you are having a difficult time with someone you love, invite him / her to watch a comedy. you will probably make peace.

laugher will certainly protect you against stress and emotional pain. watching a comedy   may be a solution to stress or damaged bonds. " this remedy is fun , free, and best of all, no instructions needed."   alannagh kelly has said in her blog.