In this level, we take ten verbs and put them in the past tense by adding an -ed ending to them.

Two exceptions, though: First, if the verb already ends with an e (such as compare), we just add the letter d to put the verb in the past tense.

Second, if the verb ends with a short vowel and then a single consonant other than x (such as stop), the final consonant is generally doubled before the -ed ending is added. So stop becomes stopped instead of stoped.