单选题：What is the value of `s2` after this code executes?

What is the value of `s2` after this code executes? @[C](2)
```Java
String s1 = "Happy#day";
String s2 = s1.substring(1,5);
```

A. "Happ"
B. "Happy"
C. "appy"
D. "appy#"



A."Happ"
B."Happy"
C."appy"
D."appy#"


答案：C