The migration of the monarch butterflies
For questions 1-8, read the text below and decide which answer ( A, B, C or D ) best fits each gap. There is an example at the beginning ( 0 ).
Example:
The migration of millions of North American monarch butterflies is one of the most stunning 0 _____ phenomena on Earth. In 1 (1) ____ to other members of the same species elsewhere, the North American species migrates far in winter, taking a journey that 2 (2) ____ of 3000 miles. They 3 (3) ____ off in Canada and the US, arrive in central Mexico in November, and return in March. The sight of them together in fir trees in Mexico is an incredible 4 (4) ____ to witness.
However, none of the butterflies actually make the entire round trip. The females lay eggs in Mexico and it’s the new generation that heads north. They travel to Texas where the process is repeated. The butterflies have a 5 (5) ____ to stop twice on their way back to Canada, meaning that it takes four generations to complete the trip.
Monarch butterflies are important because they pollinate plants. In 6 (6) ____, they form a key part of the food chain. They also 7 (7) ____ danger from disease and a loss of habitat. However, at 8 (8) ____ their forest in Mexico is protected.