Be careful of that vase! Be careful of that vase!
I always arrive on time! I always arrive in time!
(2) do can change tensely when it is used to express emphasis, but the verb behind it should be in its original form. For example:
He really speaks very well! He did speak brilliantly.
He did come, but he went back soon. He did come, but he went back soon.
Do used for emphasis is usually only used in the present tense or past tense (that is, it is only used in forms such as do, does, did did, etc.), and cannot be used in forms such as continuous tense and perfect tense (such as not used in As Do, h as do, etc.). ).
In addition, do is often used in imperative sentences to express emphasis. For example:
(1) indicates a request for emphasis. For example:
Be sure to come with us. Please be sure to come with us.
Please. Please be quiet for a while! Please. Be quiet for a while!
(2) Express euphemism or politeness. For example:
Be sure to try this fish. Please try this fish.
Another cup of coffee, please. Another cup of coffee, please.
(3) show impatience. For example:
Don't talk! Stop it!
(4) I hope to convince the other party. For example:
Be sure to help me solve this math problem. Please help me solve this math problem.