Hi all,
I got a trouble in Sync.The code is as follows:
apply plugin: 'com.android.application'
android {
    compileSdkVersion 28
    buildToolsVersion '25.0.3'
    defaultConfig {
        applicationId "com.bignerdranch.android.geoquiz"
        minSdkVersion 19
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}
dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:28.0.0'
    testCompile 'junit:junit:4.13-beta-3'
}
And the hints are like this:

I’ve tried so many solutions but in vain. Please help me! Thank you so much!