Final answer:
The correct answer uses the present continuous tense 'is doing,' indicating that Frederick is presently engaged in the action of doing his homework, which is why he cannot come.
Step-by-step explanation:
The correct sentence should be: Frederick can't come because he is doing his homework. It uses the present continuous tense, indicating that Frederick is currently in the middle of doing his homework, which prevents him from being able to come.
Grammar and Verb Tense
Understanding the use of the present continuous tense is essential to construct sentences that describe ongoing actions. It is formed using the verb 'to be' in the present tense (is/am/are), followed by the '-ing' form of the main verb. This tense is often used to describe something that is happening at the moment of speaking or at the current period of time.
Examples of Present Continuous Tense
- She is reading a book right now.
- They are playing soccer in the park.
- He is working on the project all weekend.