Marcar texto Android Studio

<ScrollView xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">


    <ImageView
        android:id="@+id/bookthumbnail"
        android:layout_width="125dp"
        android:layout_height="170dp"
        android:layout_marginTop="10dp"
        android:background="#2d2d2d"
        android:gravity="center"
        android:layout_centerHorizontal="true"
        android:scaleType="centerCrop" />

    <TextView
        android:id="@+id/txttitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Book Title"
        android:textSize="12sp"
        android:textStyle="bold"
        android:gravity="center"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/bookthumbnail"
        />

    <TextView
        android:id="@+id/txtCat"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Category"
        android:background="#edecec"
        android:padding="8dp"
        android:gravity="center"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/txttitle"
        />

    <TextView
    android:id="@+id/txtDesc"
    android:textSize="18sp"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="Description"
    android:gravity="center"
    android:layout_below="@+id/txtCat"/>

<TextView
    android:id="@+id/txtDesc01"
    android:textSize="18sp"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="Description01"
    android:gravity="center"
    android:layout_below="@+id/txtDesc"/>

    <TextView
        android:id="@+id/txtDesc02"
        android:textSize="18sp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Description02"
        android:gravity="center"
        android:layout_below="@+id/txtDesc01"/>

    <TextView
        android:id="@+id/txtDesc03"
        android:textSize="18sp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Description03"
        android:gravity="center"
        android:layout_below="@+id/txtDesc02"/>

    <TextView
        android:id="@+id/txtDesc04"
        android:textSize="18sp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Description04"
        android:gravity="center"
        android:layout_below="@+id/txtDesc03"/>

    <TextView
        android:id="@+id/txtDesc05"
        android:textSize="18sp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Description05"
        android:gravity="center"
        android:layout_below="@+id/txtDesc04"/>

    <TextView
        android:id="@+id/txtDesc06"
        android:textSize="18sp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Description06"
        android:gravity="center"
        android:layout_below="@+id/txtDesc05"/>

</RelativeLayout>
</ScrollView>