Introduce the two key phrases for talking about preferences 'would rather' and 'would prefer' by giving examples and asking questions such as 'would you prefer to eat pizza or pasta for dinner tonight?', or 'I would rather swim with sharks than hold a snake'.
After the students have understood the concept, write out each phrase and show them that there are certain rules for how to complete the sentence:
'Would rather...' should be followed by an infinitive without the 'to'
'Would prefer...' should be followed by an infinitive or present continuous.
Have them complete the worksheet paying attention to the forms of the verbs that follow the gap, in order to choose whether to insert 'would rather' or 'would prefer'. Have them areas each sentence out loud to get familiar with how they sound.
This topic can easily be reviewed or reinforced by asking thought-provoking 'would you rather...' hypothetical questions.
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