Add a drop down list to single product options

I am trying to figure out how to modify the singe product options so the product admin can pick from the drop down list the condition of product, i.e. new/ used.

Below is a code that allows product admin to enter the condition of product manually.

// Enabling and Displaying Fields in backend add_action( 'woocommerce_product_options_general_product_data', 'woo_add_custom_general_fields' ); function woo_add_custom_general_fields() { global $woocommerce, $post;

echo '<div class="options_group">';

woocommerce_wp_text_input( array( // Text Field type
    'id'          => '_Stan', 
    'label'       => __( 'Stan', 'woocommerce' ), 
    'placeholder' => 'i.e: nowa; uzywana...',
    'desc_tip'    => 'true',
    'description' => __( 'Podaj stan plyty.', 'woocommerce' ) 
) );

echo '</div>'; // Closing </div> tag HERE
}

// Save Fields values to database when submitted (Backend) add_action( 'woocommerce_process_product_meta', 'woo_save_custom_general_fields' ); function woo_save_custom_general_fields( $post_id ){

// Saving "Conditions" field key/value
$Stan_field = $_POST['_Stan'];
if( !empty( $Stan_field ) )
    update_post_meta( $post_id, '_Stan', esc_attr( $Stan_field ) );
} add_action('woocommerce_single_product_summary', 'woo_display_custom_general_fields_values', 45); function woo_display_custom_general_fields_values() { global $product;

echo '<p class="custom-Stan">Stan: ' . get_post_meta( $product->id, '_Stan', true ) . '</p>';

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