Which of the following definitions of the WP_DEBUG constant can be used to trigger the debug mode throughout WordPress?

Which of the following definitions of the WP_DEBUG constant can be used to trigger the debug mode throughout WordPress?

• define( ‘WP_DEBUG’, true);
• define( ‘WP_DEBUG’, ‘true’);
• define(‘WP_DEBUG’, ‘1’);
• define(‘WP_DEBUG’,”true” );