Last night I received an email from a reader who wanted me to clarify that is possible to grade short answer questions in the default "quizzes" mode. When you are selecting quiz settings in Google Forms you will need to choose the option for releasing grades "later, after manual review." Then you will need to manually score your students' responses to your short answer questions.
Another way to accept and score fill-in-the-blank and short answer questions in Google Forms is to use the Google Sheets Add-on called Flubaroo for scoring responses. Flubaroo will let you have fill-in-the-blank responses automatically scored. When you create an answer key in Flubaroo you can specify one or more correct responses for each question. If you enable the automatic grading option in Flubaroo, students can receive their grades within seconds of submitting their final answers.
Join my January 4th webinar Google Forms for Beginners to learn more about how to create and grade assessments in Google Forms.