What is the difference in mean solar time between 30 N 75 W and 30 N 90 W​

The wave shown on the electromagnetic spectrum disturb the medium it passes through a)different frequency. b)the same frequency .

How are isotopes of the same chemical element alike? how are they different?

Pastoral farming is best described as a. a method of raising livestock and moving herds b. an african method of agriculture c. a method of cultivating crops on poor soils d. a common method of desert farming select the best answer from the choices provided a b c d