I need an answer someone please help the subject i digital citizenship

How many liters of 60% alcohol solution should be added to 40 liters of a 20% alcohol solution to make a 50% solution?

In an ecosystem, marsh snails feed on phytoplankton and painted turtles feed on marsh snails. pollution has resulted in the depletion of phytoplankton. what effect would this situation likely have on the population of marsh snails and painted turtles? as phytoplankton were destroyed, the population of marsh snails would most likely then the population of painted turtles would mostly likely a. 1. increase 2. decrease 3. stay the same b. 1. increase 2. decrease 3. stay the same

How are 3-d printers useful in studying evolution? a. to color the fossils of organisms b. to create clones of extinct organisms c. to create replicas of fossils d. to prepare paper cutouts of organisms e. to study the composition of fossils