Rust-所有权和借款

Question

我试图学习生锈，并陷入所有权和借贷问题。

let s1 = String::from("Hello");
let s2 = s1;
print!("{}", s1); //---> Why this is an error ?

let a = "hello";
let b = a;
print!("{}", a); //--> But why this is not ?

有人可以帮我这个忙吗？