Answer:
1. If <u>you </u><em><u>happened</u></em><u> to go</u> to the shops, could you buy me some toothpaste?
2. They'll return his money <u>as </u><em><u>long</u></em><u> as he has</u> the original receipt.
3. We won't be able to go to Paris <em><u>unless</u></em><u> we have enough</u> money.
4. <u>If </u><em><u>only</u></em><u> we had gone</u> to the party yesterday.
5. You'll be able to contact her any time <u>in </u><em><u>case</u></em><u> you need</u> her help.
Explanation:
1. If <u>you happened to go</u> to the shops, could you buy me some toothpaste?
In this sentence, "happened" is used to mean the same intention of asking for help.
2. They'll return his money <u>as long as he has</u> the original receipt.
The use of the phrase "as long as" presents a valid reason for why or how the refund will be given, which is the same as "but only if".
3. We won't be able to go to Paris <u>unless we have enough</u> money.
"Unless" is and can be used to mean the same as "if" for it presents a condition for a successful 'action/result'.
4. <u>If only we had gone</u> to the party yesterday.
Using "if only" in the sentence presents the same feeling of regret in "what a shame".
5. You'll be able to contact her any time <u>in case you need</u> her help.
The use of the phrase "in case" presents the same intention of a need and replaced the word "because".
