What is a drought? what problem can it cause?

Researchers want to use edna to look for an invasive species in the water which of the steps would be likely do last

Select the situation bellow that would produce a total displacement of zero. a. a trip to the moon and then to mars b. a horse galloping from one end of a field to another c. the criss-crossing path of a bug as it flies from flower to flower d.a round-trip ride to school and back

Based on their relative positions in the periodic table, which two elements would have the same number of valence electrons?