Pasiv (Passive Voice)

Read the text below. For each question (25-32), choose the answer (A, B, C or D) that best completes the sentence.

Sleeping Octopuses

Octopuses may be many mariners' nightmares, but new research has added to growing evidence that they may dream while asleep.

Octopuses (25) ____ to undergo two different stages of sleep: 'quiet sleep' and 'active sleep', the latter of which involves twitching body parts and rapid changes in the texture and patterning of the skin.

Researchers (26) ____ the Japanese Institute of Science claim – in addition to confirming that octopuses do indeed sleep during this active stage – they have also discovered that this stage shares many characteristics with REM sleep in humans.

Prof. Tom Roody, the study's lead author, said the team's findings were not proof that octopuses dream. "Perhaps we (27) ____ already associate certain skin patterns during wakefulness to particular situations: hunting, social displays, threat displays, and camouflage to different sorts of environments. These patterns reappear during active sleep," he said. "So, if we are looking at something like dreaming, (28) ____ I repeat, this is a possibility we do not prove in this study, they would resemble a pseudo random walk over waking experiences."

However, Roody put (29) ____ that there are other possible explanations: for example, that octopuses refine their camouflage patterns while they sleep.

When the team tapped on the tanks and watched how the animals responded, they found the octopuses showed different reactions depending on whether they were awake, in the quiet stage of sleep, or in the active stage. Every 60 minutes or so, the animals (30) ____ rapid changes of skin colour that lasted about one minute, together with changes in breathing rate, as well as body and eye movements.

What's more, if the octopuses were deprived (31) ____ sleep for two days by being tickled with a paintbrush, they subsequently showed an increased rate of active sleep. They entered the stage sooner, (32) ____ a self-regulating control – one of the key criteria of sleep.

The researchers confirmed that octopuses were indeed asleep during the active stage.