An inference is an idea or conclusion that's drawn from evidence and reasoning. An inference is an educated guess.
Think about the following sentences. Think of as many reasons as you can as to why they happened. If you like, imagine you are Sherlock Holmes.
01. I forgot to set my alarm clock
02. The boat drifted on the lake.
03. John ran into the street without looking.
04. Everyone stopped when the referee blew the whistle.
05. She blew out the candles.
06. Emily sat in her bedroom and began to cry.
07. The man has dirty knees.
08. Edward had a much bigger breakfast than usual.
09. Natasha is eating at her favourite restaurant.
10. The bookshop doors were open at midnight.
e.g 01 Maybe they were drunk or just forgot.
As a follow on for this activity you could discuss what happens next in the situations.