Asurvey shows that 45% of the respondents pick option a. given that 50 people replied, what is the standard error of the proportion?

the choices are
a. 7.04%
b. 14.06%
c. 21.09%
d. 0.07%

There are several important information's already given in the question. Based on those given information's the answer can be easily deduced.
Standard error = square root[ (0.45 * 0.55)/50]
                        = square root (0.2475/50)
                        = square root (0.00495)
                        = 0.07 percent

From the above deduction, it can be easily concluded that the correct option among all the options that are given in the question is the fourth option or option "D". I hope that this is the answer that has actually come to your desired help.