阅读下面这篇短文，短文后有2项测试任务：(1)第23～26题要求从所给的6个选项中为规定段每段选择1个正确的小标题；(2)第27～30题要求从所给的6个选项中选择4个正确选项，分别完成每个句子。
Every year thousands of grey whales make the longest
migration of any animal, traveling 7,000 miles each way between the Arctic and
Baja, California. The grey whales spend the long summer days in their Arctic
feeding grounds in the Bering Sea between Alaska and Russia. Unlike a fish, the
whale is warm-blooded and must therefore maintain a relatively high internal
body temperature. In the cold Arctic waters the grey whale is protected by an
outer layer of blubber which averages six inches in thickness. Other whales such
as the Greenland Night whale have been found with a two-foot thick layer of
blubber covering their bodies. 2. During these summer months,
in the Arctic the grey whales fatten themselves by consuming enormous quantities
of small shrimp-like animals called amphipods. Recent observations of a young
grey whale, Gigi Ⅱ, held in captivity at Sea World in San Diego during 1971 and
1972, suggest that the grey whale feeds by sweeping its enormous head over the
bottom. The amphipods on which it feeds are either stirred off the bottom or
leap off the bottom to escape. These animals and the surrounding water are
sucked into the whale’s mouth. As the water is expelled from the mouth, it
passes through coarse baleen fibres. The small animals are trapped and
swallowed. 3. In October as the days get shorter and ice begins
to form over the Arctic feeding grounds, the California grey whale begins its
long journey south to the warm waters of Baja, California. During this
three-month long trip the whales travelling in groups stay close to the shore of
North America, swimming both day and night and averaging abut 100 miles per
day. 4 During the trip south the grey whales that are sexually
mature, at least three years old, and not pregnant already, form mating groups.
These groups are composed of three whales, two males and a female. The dominant
male couples with the female while the second male is kept busy positioning the
two whales on their sides facing each other and keeping them together during the
sex act. This is no small job, since each whale can be fifty feet long and weigh
forty tons. 5. During December and January the grey whales
arrive at the warm lagoons along the coast of Baja, California. The whales swim
miles inland along narrow shallow channels. These channels are the breeding
grounds of the California grey whale. The calf has been gestating in the
pregnant female for the last thirteen months, that is, since her last journey
south. The expectant cow is aided in the birth of the calf by another female
that acts as a midwife. At birth the calf sinks toward the sea floor. Being a
mammal the whale must breathe at the surface. The midwife guides the baby whale
to the surface for its first gulp of air. The calf then finds its mother’s
nipples and rich whale milk is forced into its mouth. During the next two months
the calf will grow twenty feet and double its weight. 6. In
March the whales begin their long journey north to the Arctic. The
newly-pregnant females leave first, following by the males and immature females.
The last to leave the warm waters of Baja are the females and their calves. The
whales arrive at their Arctic feeding ground in June. Many scientists believe
that during this entire eight month long, 14,000 mile journey, the California
grey whale does not feed at all! Paragraph 5 ______