The word do is used here for emphasis

[Elkalotis]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #116 "Future Tenses", question 5

If they ......... arrive late, they will have to get their own meal.

(a) do
(b) had
(c) would
(d) will

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #116 "Future Tenses", answer 5

If they do arrive late, they will have to get their own meal.

Correct answer: (a) do

Your answer was: incorrect
If they would arrive late, they will have to get their own meal.
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dear sir

I think we dont need word (do,would...ect) in sentence
base: if+present, future

Elkalotis

[Alan]

Hi,

The word do is used here for emphasis. It's the same construction as: If they arrive late .....

Look at this examples:

If I do come, I'll bring some food.

This means it's not absolutely definite that I will come but in the event that I come, I'll bring some food.

Alan
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English as a Second Language
You can read my ESL story Present Simple