Read the following passage and mark the letter A, B, C, or D on your answer sheet to choose the word or phrase that best fits each of the numbered blanks from 26 to 30.

Humans are harming dolphins at an alarming rate. Long fishing nets known as 'Walls of Death' are mainly to (26) ________. Since their introduction in the 1960s, millions of dolphins, whales and seals have been accidentally caught up in them and killed. The nets are used by fishermen operating illegally (27)
________ want to increase the size of their catch. They are dropped into the sea at night where they catch anything that is fortunate enough to get in their way.
This is a very economical method of fishing, as (28) ________ fish are lost or injured when the nets are hauled in. As the nets are almost invisible, the dolphins have difficulty in seeing them and so are lured to their death. Fortunately, there are now a number of charities who are working to (29) ________ awareness of this issue. Their work is helping the conservation of dolphins, (30) ________ hopefully this destruction may soon be stopped.
(Adapted from FCE Use of English)