Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions from 44 to 50.

In a paper published in Science Advances, an international team of researchers have examined traits of marine megafauna species to better understand the potential ecological consequences of their extinction under different future scenarios.

Defined as the largest animals in the oceans, with a body mass that exceeds 45kg, examples include sharks, whales, seals and sea turtles. These species serve key roles in ecosystems, including the consumption of large amounts of biomass, transporting nutrients across habitats, connecting ocean ecosystems, and physically modifying habitats. Traits, such as how large they are, what they eat, and how far they move, determine species’ ecological functions. As a result, measuring the diversity of traits allows scientists to quantify the contributions of marine megafauna to ecosystems and assess the potential consequences of their extinction.

The team of researchers – led by Swansea University’s Dr Catalina Pimiento – first compiled a species-level trait dataset for all known marine megafauna to understand the extent of ecological functions they perform in marine systems. Then, after simulating future extinction scenarios and quantifying the potential impact of species loss on functional diversity, they introduced a new index (FUSE) to inform conservation priorities.

The results showed a diverse range of functional traits held by marine megafauna, as well as how the current extinction crisis might affect their functional diversity. If current trajectories are maintained, in the next 100 years we could lose, on average, 18% of marine megafauna species, which will translate in the loss of 11% of the extent of ecological functions. Nevertheless, if all currently threatened species were to go extinct, we could lose 40% of species and 48% of the extent of ecological functions. Sharks are predicted to be the most affected, with losses of functional richness far beyond those expected under random extinctions.

(Adapted from https://www.sciencedaily.com/)

The word “they” in paragraph 3 refers to _____________.