Is "at the same time" preceded by a period or a comma?

? Period, because while is an adverb, not a conjunction. Adverbs cannot be used to connect independent sentences.

If the following sentence is short, such as "Our most common words are composed of two words, such as happy, funny, and so on." Commas are generally used.

We clearly remember that it was the spring of 1952. When Jindalai in Shan Ye was in bloom, you knew we were short of vegetables, so you went up the mountain with baskets to dig wild vegetables.

The prepared pilaf is bright in color and delicious in taste. It is worth mentioning that the carrots in pilaf are rich in carotene, which has a very good effect on protecting eyesight.

Pilaf is a kind of food that Xinjiang people like very much. The raw materials of pilaf are fresh mutton, carrot, onion, clear oil, sheep oil and rice. The practice is to chop the mutton into small pieces, fry it in clear oil, then fry the onions and carrots in a pot, and add some salt and water appropriately. After 20 minutes, put the soaked rice into the pot without stirring. After 40 minutes, grab the rice and it will be cooked.