<p-dropdown> display list of data which is binded with [Options]

I am working on angular6 project. I am using primeng for design. following dependencies, I have added into package.json.

"dependencies": {
    "@angular/animations": "6.0.9",
    "@angular/common": "6.0.9",
    "@angular/compiler": "6.0.9",
    "@angular/core": "6.0.9",
    "@angular/forms": "6.0.9",
    "@angular/http": "6.0.9",
    "@angular/platform-browser": "6.0.9",
    "@angular/platform-browser-dynamic": "6.0.9",
    "@angular/router": "6.0.9",
    "@ng-bootstrap/ng-bootstrap": "^3.0.0",
    "angular-6-datatable": "^0.8.0",
    "core-js": "^2.4.1",
    "ngx-bootstrap": "^3.0.1",
    "primeicons": "^1.0.0",
    "primeng": "^6.1.3",
    "rxjs": "^6.2.2",
    "zone.js": "^0.8.26"
  }

I have added below module of primeng in apapp.module.ts.

import { AccordionModule} from 'primeng/accordion';    
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { DropdownModule } from 'primeng/primeng';

I have creat one component and use . HTML file for it as below.

<div>
   <p-dropdown [options]="dataTypeList" [(ngModel)]="selectedDataType" placeholder="select data type" optionLabel="name" [showClear]="true" [ngModelOptions]="{standalone: true}"></p-dropdown>
</div>

Component file is as below.

interface DataType{
    name: String,
    code: String
}
export class MyComponent{
    private dataTypeList: DataType[];
    private selectedDataType: DataType;
    constructor(){
        this.dataTypeList=[
            {name:'String', code:'1'},
            {name:'Integer',code:'2'}
        ];
    }
}

I have followed all step of primeng of primeng documentation and primeng dropdown documentation. As a output, I am expecting single dropdown list there. But I got one extra textBox below dropdown and when I am clicking on that textBox all data has been displayed at the bottom which is binded with <p-dropdown> which is shown as below image. When I removed <p-dropdown> from the code extra output also removed.

enter image description here

enter image description here