В приведенном ниже тексте на место пропуска (4) нужно добавить прилагательное в нужной степени сравнения ... The Channel Tunnel is the second 1)... (long) tunnel in the world. The 2)... (long) is the Seikan tunnel in Japan, but the Channel Tunnel has a 3)... (long) undersea section. One team began drilling in France and the other in England. The drilling machines were 4)... (heavy) ever made. The 5)... (big) problem for the builders was to meet at exactly the same place in the middle of the Channel. The Channel Tunnel is 6)... (great) engineering project ever. It has 7) ... (sophisticated) railway control system in the world, and it's going to be 8)... (busy) railway track in Europe, with one train every three minutes.

Решение:

Пропуск (4) требует сравнительной степени прилагательного 'heavy', которая будет 'heavier'. Так как далее идет 'ever made', это указывает на превосходную степень. Поэтому правильный вариант — the heaviest.

Ответ: the heaviest