In July 1994 the comet Shoemaker-Levy 9 collided with
the planet Jupiter, as scientists had
predicted. To be able to accurately
predict when a comet will collide with a
planet, it is essential to understand-
A. the composition of a planet's
atmosphere
B. the gravitational attraction that
exists between all bodies
C. the attraction of opposite poles of a
magnet to each other
D. the formation of comets

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

the endomembrane system i think

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.