Choose the function whose graph is given by:

using a graph tool

I proceed to graph each case

case a)

see the attached figure N 1

case b)

see the attached figure N 2

case c)

see the attached figure N 3

case d)

see the attached figure N 4

therefore

the answer is the option A

The period of the function is . From the graph you can see that period of given function is (you can see that at x=0, y=1 and next time y=1 when x=4π ).

Then 

.

For the function becomes .

correct choice is A.

change of stock price/initial stock price on friday * total stock value = change of stock value

0.89/73.73 *x = 42.72

x=3539.04 = total stock value at initial stock price on friday .

total stock value at initial stock price on friday/ initial stock price on friday = number of shares

3539.04/73.73 = 48 shares

they own 48 shares of this stock

0.61 has 2 decimal places, so we put the decimal digits of 0.61, 61 over 1 followed by the number of zeroes equal to the number of decimal places, 

2:     61/1 = 61/100.