The correct answer for the question is option 4, "chars". Chars are known as the uplands of delta regions.

Option 1, "Bef", is not the correct answer. There is no mention of "Bef" in the context of uplands in the delta region.

Option 2, "Bils", is not the correct answer. "Bils" is also not mentioned as the uplands in the delta region.

Option 3, "Peh", is not the correct answer. Similarly, there is no reference to "Peh" being the uplands of the delta region.

Option 4, "chars", is the correct answer as it refers to the uplands of the delta regions. Chars are elevated areas or islands that form as a result of sediment deposition in river deltas.

In conclusion, the uplands of the delta region are known as chars.