What are countermeasures? Are they technical in nature, or non-technical as well?

An education expert is researching teaching methods and wishes to interview teachers from a particular school district. she randomly selects ten schools from the district and interviews all of the teachers at the selected schools. which type of sample did she use in this study? a)systematic sample b)probability sample c)stratified sample d)cluster sample

The united states economy is one in which producers are generally free to produce what they want and consumers are free to purchase what they desire, so long as no laws are broken. at the same time, however, the government does regulate some aspects of the economy. the u.s. can best be described as which of the following a mixed economy b liberated economy c command economy d market economy

Often, a goby fish and a shrimp will live together in a burrow the shrimp has dug in the sand. the shrimp is almost blind and therefore is unable to see predators approaching when he is outside of the burrow. when the shrimp is in danger, the goby fish touches the shrimp with its tail to warn him. then, both go back into their burrow for safety. which type of relationship does this represent? a. mutualism b. parasitism c. commensalism d. predator/prey