在Angular 4到9中，可以使用HttpClient模块来发送HTTP请求。以下是一些常用的请求选项以及相应的代码示例：

1. 发送GET请求：

import { HttpClient } from '@angular/common/http';

constructor(private http: HttpClient) { }

// 发送GET请求
this.http.get('https://api.example.com/data')
  .subscribe(response => {
    console.log(response);
  });

2. 发送带参数的GET请求：

import { HttpClient, HttpParams } from '@angular/common/http';

constructor(private http: HttpClient) { }

// 发送带参数的GET请求
const params = new HttpParams().set('param1', 'value1').set('param2', 'value2');
this.http.get('https://api.example.com/data', { params })
  .subscribe(response => {
    console.log(response);
  });

3. 发送POST请求：

import { HttpClient } from '@angular/common/http';

constructor(private http: HttpClient) { }

// 发送POST请求
const data = { name: 'John', age: 30 };
this.http.post('https://api.example.com/data', data)
  .subscribe(response => {
    console.log(response);
  });

4. 发送带请求头的请求：

import { HttpClient, HttpHeaders } from '@angular/common/http';

constructor(private http: HttpClient) { }

// 发送带请求头的请求
const headers = new HttpHeaders().set('Authorization', 'Bearer token');
this.http.get('https://api.example.com/data', { headers })
  .subscribe(response => {
    console.log(response);
  });

5. 发送带身份验证的请求：

import { HttpClient, HttpParams } from '@angular/common/http';

constructor(private http: HttpClient) { }

// 发送带身份验证的请求
const params = new HttpParams().set('param1', 'value1').set('param2', 'value2');
const options = { params, withCredentials: true };
this.http.get('https://api.example.com/data', options)
  .subscribe(response => {
    console.log(response);
  });

这些是一些常用的请求选项，可以根据具体需求进行调整和扩展。