WordPress get_option to variable without use of undefined constant

My plugin i have many options. I use get_option and store it as an array so its easier to use.

function woomps_get_options() {
    $options = array(
        'sub01' => get_option(woomps_sub01),
        'sub02' => get_option(woomps_sub02),
        );
    return $options;
}

This produces this notice for each line:

[TIME] PHP Notice:  Use of undefined constant woomps_sub01 - assumed 'woomps_sub01' in "DOMAIN"settingsoptions.php on line 9

I dont understand why i should define woomps_sub01 first or how i should define it. But my question is rather: Why is this not a correct way to get a WP option and what is the better way?