Review the code snippet below:

sentence $=$ input $("$Enter some text: $")$

firstch $=$ sentence $0$

Which of the following statements correctly determines if the first letter of the string contained in sentence is an uppercase letter?

if firstCh. isupper$()$ :

if not $($firstCh$.$isupper$())$ :

if firstCh.isspace$()$ :

if not $($firstCh$.$isspace$())$ :