Final answer:
In English, combining verbs with modals like must, may/might/could, and can express different modalities or degrees of certainty, while 'should' suggests a recommendation or obligation.
Step-by-step explanation:
In English grammar, modals are auxiliary verbs that express necessity, possibility, permission, or ability. When you use the verb in parentheses with the modals must, may/might/could, can, and should, you are conveying different degrees of likelihood or obligation. For example, in the sentence 'I could finish my essay by eight o'clock tonight,' the verb 'finish' is combined with the modal 'could,' showing a possibility. When an action is required, the modal 'must' is used without a past form, as in 'You must submit your request on time.' On the other hand, when making polite suggestions or obligations that are not as strong as 'must,' 'should' is used, such as 'You should check your answers before submitting the test.'
Understanding verb mood is important in crafting your sentences appropriately. The indicative mood is for stating facts, the imperative for giving commands, and the subjunctive for expressing wishes, suggestions, or conditions contrary to fact. It is also important to maintain verb tense consistency within your writing to ensure clarity and precision.