Final answer:
To change the word 'shop' to its past tense, add -ed and double the final consonant.
Step-by-step explanation:
To change the underlined word 'shop' to its past tense, we need to add -ed at the end. However, since the word 'shop' ends with a consonant, we need to double the final consonant before adding -ed. Therefore, the correct past tense of the sentence 'We shop all day today' is 'We shopped all day today'.
Learn more about Past tense with double consonants