Can you help explain static lifetime in hyper in rust?

Question

I am using hyper and I am confuse with some codes.

My code is like

 self.hyper_client = ...

 match Request::builder()
        .method(Method::POST)
        .uri(uri)
        .header("content-type", "application/json")
        .body(Body::from(serde_json::to_string(&content).unwrap()))
    {
        Ok(req) => {
            match self.hyper_client.request(req).await
        },
        Err(err) => {
            ...
        }
    }

First I think the req object generated by Request::builder is not static lifetime right?

But in client.request function, the prototype is pub fn request(&self, mut req: Request<B>) -> ResponseFuture and Client's B is

impl<C, B> Client<C, B>
where
    C: Connect + Clone + Send + Sync + 'static,
    B: HttpBody + Send + 'static,
    B::Data: Send,
    B::Error: Into<Box<dyn StdError + Send + Sync>>,
{
....

it seems B should be static?

I am confused about static lifetime, can you help me about it?

Thanks.