"The majority of shoplifters seem to be youngsters, middle-aged or even elderly people who, in a moment of confusion,
................ (slip) something into their bags and ................. (forget) to pay for it. Some stores are in fact doing their best to separate the real thieves from those who have no intention of stealing."

Please advise what are the correct answers.

What if both the present & past tenses are given as answers by some students? (i.e 'slip and forget'; 'slipped and forgot')
Which is correct bearing in mind the present tense of the sentence? (or both are correct)
Some students might use the past tense because the shoppers will become shoplifters only after they have slipped the thing into their bags & forgotten to pay (i.e done the act first).

Will appreciate answers soonest. Many thanks.
Either past or present is o.k., as long as they are the same tense in the sentence. There are some who might argue that for the verbs in question to be in the past, the phrase "majority of shoplifters seemed to be....." would be appropriate. I don't think so.
I'd choose the present tense too. They become shoplifters at the moment they "slip something" into their bags. Also, if we use the past tense, there's a slight discord later with "who have no intention of stealing".

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I see no reason to use any past tenses there, given that there are no others in the entire passage.
The studied approach of "the shoppers will become shoplifters only after they have slipped ..." is what I would call "borrowing trouble" or perhaps "digging too deep"! Emotion: smile

 MrPedantic's reply was promoted to an answer.
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