In each question, the first and the last sentences of the passage are numbered S1 and S6 respectively. The rest of the passage is split into four parts. These four sentences are jumbled. Read the sentences and identify their correct and logical order.

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S1: Frozen foods are so popular today that many people wonder how they ever lived without them.
P: Near the North Pole, where the ground stays frozen all the year around, there is no problem of preserving foods.
Q: Actually, people who live in cool climates have had frozen foods for a long time.
R: Ice helped them when they could get it, but they couldn't get it very often.
S: But people who live in warm climates have not always been able to keep food fresh.
S6: Now refrigerators and deep freezers preserve many foods that could not be kept any other way.
The Proper sequence should be: