未捕获错误：模块'AppModule'导入的意外值'AngularFireDatabase' . 请添加@NgModule注释

嗨，我是角度和firebase的新手，我从今天早上起就一直在努力解决一个简单的代码问题，我搜索了这个问题，但我找不到任何对我有用的解决方案（有时候我甚至都不懂它，我是一个真正的初学者）我在控制台上的错误如下：

未捕获错误：模块'AppModule'导入的意外值'AngularFireDatabase' . 请添加@NgModule注释 . 在位于eval（compiler.js：15225）的syntaxError（compiler.js：485）处，位于JitCompiler._compileModuleAndComponents的JitCompiler._loadModules（compiler.js：34255）的CompileMetadataResolver.getNgModuleMetadata（compiler.js：15200）的Array.forEach（）处（compiler.js：34216）位于Eval（main.ts）的PlatformRef.bootstrapModule（core.js：5568）的CompilerImpl.compileModuleAsync（platform-browser-dynamic.js：230）上的JitCompiler.compileModuleAsync（compiler.js：34110） ：11）

这是我的代码： the app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AngularFireModule } from "angularfire2";
import { AngularFireDatabaseModule, AngularFireDatabase } from "angularfire2/database";
import { AppComponent } from './app.component';
import { environment } from '../environments/environment';


@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    AngularFireModule.initializeApp(environment.firebase),
    AngularFireDatabase    
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

the app.component.ts

import { Component } from '@angular/core';

import { Observable } from 'rxjs/Observable';
import { AngularFireDatabase } from "angularfire2/database";

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {

   }
}

the dependencies of the package.json

"dependencies": {
    "@angular/animations": "^5.0.0",
    "@angular/common": "^5.0.0",
    "@angular/compiler": "^5.0.0",
    "@angular/core": "^5.0.0",
    "@angular/forms": "^5.0.0",
    "@angular/http": "^5.0.0",
    "@angular/platform-browser": "^5.0.0",
    "@angular/platform-browser-dynamic": "^5.0.0",
    "@angular/platform-server": "^5.1.2",
    "@angular/router": "^5.0.0",
    "@angular/service-worker": "^5.1.2",
    "angularfire2": "^5.0.0-rc.4",
    "core-js": "^2.4.1",
    "firebase": "4.8.0",
    "ng-push": "^0.2.1",
    "ng-pwa-tools": "0.0.15",
    "rxjs": "^5.5.2",
    "webpack": "^3.10.0",
    "zone.js": "^0.8.14"
  },
  "devDependencies": {
    "@angular/cli": "^1.6.2",
    "@angular/compiler-cli": "^5.0.0",
    "@angular/language-service": "^5.0.0",
    "@types/jasmine": "~2.5.53",
    "@types/jasminewd2": "~2.0.2",
    "@types/node": "~6.0.60",
    "codelyzer": "^4.0.1",
    "jasmine-core": "~2.6.2",
    "jasmine-spec-reporter": "~4.1.0",
    "karma": "~1.7.0",
    "karma-chrome-launcher": "~2.1.1",
    "karma-cli": "~1.0.1",
    "karma-coverage-istanbul-reporter": "^1.2.1",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.2",
    "ts-node": "~3.2.0",
    "tslint": "~5.7.0",
    "typescript": "~2.4.2"
  }

我试图重新安装所有的东西，但似乎没有任何工作，我希望你们可以帮助我