In Quiz, with short answers,
at the moment, when the expected answer is "the cat" and the received answer is " the cat" the answer is considered as wrong. Joseph Réseau has created a parch that works for M1.9 and Tim Hunt sees no reason why it should not be made standard in M2. (see here :https://moodle.org/mod/forum/discuss.php?d=272781#p1174176).
Besides, another trimming should be: removing extra spaces before punctuation; so that when the expected answer is "The sun is shining." an answer such as "The sun is shining ." would be accepted.
Many thanks for looking into this.