E. Underline the correct particle. 26. I ran into / out of an old friend today
27. We're looking after / forward to our summer holidays.
28. Rea looks after / for her sister's dog when she is away.
29. If you don't know what this word means, look it for / up in the dictionary.
30. We've run out of /after flour so we can't make a cake.​

26. I ran into / out of an old friend today.
The correct particle here is "ran into". This phrasal verb means to unexpectedly meet or see someone, so it makes sense in this context where the speaker unexpectedly encountered an old friend.

27. We're looking after / forward to our summer holidays.
The correct particle here is "looking forward to". This phrasal verb means to anticipate or be excited about something in the future, so it fits the context of the sentence where the speaker is excited about their upcoming summer holidays.

28. Rea looks after / for her sister's dog when she is away.
The correct particle here is "looks after". This phrasal verb means to take care of or be responsible for someone or something, so it makes sense in this context where Rea takes care of her sister's dog when she is away.

29. If you don't know what this word means, look it for / up in the dictionary.
The correct particle here is "look it up". This phrasal verb means to search for information or find the meaning of something, so it fits the context of the sentence where the speaker suggests checking the dictionary for the definition of an unknown word.

30. We've run out of /after flour so we can't make a cake.
The correct particle here is "run out of". This phrasal verb means to have no more of something, or to use up completely, so it fits the context of the sentence where the speaker has used up all the flour and can't make a cake.

By correctly identifying the appropriate particles in these sentences, we can ensure that the meaning is clear and the sentences make sense in English.