This question tests your understanding of reported speech and verb tenses. The sentence "She promised her friends..." indicates that a promise was made in the past. When we report a promise or future intention from the past, we often shift the tense. The original direct speech was likely: "I will come and see you tomorrow."

In reported speech, the future tense "will" changes to the conditional "would". The structure for such a sentence is:

Subject + promised + (object) + (that) + Subject + would + verb (base form)...

Let's apply this rule step-by-step to the given sentence:

Step 1: Identify the main clause. "She promised her friends..." This action (promising) happened in the past.

Step 2: The promise was about a future action from that past point of view. Therefore, the verbs in the blank need to reflect this "future-in-the-past" idea.

Step 3: The correct tense to use is the conditional "would" followed by the base form of the verb.

Step 4: Apply this to both verbs. The first verb is "come". With "would", it becomes "would come". The second verb is "see". It should also be in its base form after "would", but since it's connected with "and", the "would" applies to both actions. So, it is "would come and see".

Final Answer: She promised her friends she would come and see them the next day.

Related Topic: Reported Speech

Reported speech (or indirect speech) is used to tell someone what another person said. A key rule is the backshift of tenses, where the verb tense is moved back in time.

Common Tense Changes:

• Direct: "I am busy." → Reported: She said she was busy.
• Direct: "I will help." → Reported: He promised he would help.
• Direct: "I have finished." → Reported: She said she had finished.

Related Formulae

While there are no mathematical equations, the grammatical structure can be thought of as a formula:

Reporting Clause (past tense) + that + Reported Clause (one step back in tense)

Direct Future (will) → Reported Future (would)