Researchers have created a robot that has a very thin leg that is moved by cardiac (heart) cells contracting in unison. The robot, made of a polymer similar to that used in making contact lenses, is bathed in heart cells with supporting cells, which then attach to the robot and provide movement as they contract. The robot's cardiac cells, working together in synchrony, could be considered at what level in life's hierarchy of organization?

answer: c. two haploid cells

explanation:

"do a testcross with a homozygous recessive plant."

you're crazy : )

answer;

c. a tree whose roots are surrounded by wet sand.

explanation;

water stress is an important factor limiting the growth and productivity of forests.water stress is the most often cited cause of poor survival and growth of woody landscape plants.

-insufficient soil moisture is the most common form of water stress, but excess moisture that leads to poor soil aeration (hypoxia) can also result in reduced plant vitality. a tree whose roots are surrounded by wet sand would be least likely to experience water stress.