Open the brackets and put the verb in the Present Perfect Continuous tense. Don't copy the whole sentence. Write the full form of the verb. Sherry (cook) a cake for the party since morning.

The sentence requires the Present Perfect Continuous tense. This tense is formed with 'have/has been' + the present participle (verb-ing). Since 'Sherry' is third person singular, we use 'has'. The present participle of 'cook' is 'cooking'. Therefore, the correct form is 'has been cooking'.

Answer: has been cooking