Read the excerpts below and tick the correct alternative.
“[…] to sleep—is itself extraordinarily active.”
“[…] and researchers have designed ways to test each of them.”
“If someone tells you his name, […].”
“[…] when the brain\'s two memory systems—the hippocampus and the neocortex—"talk" with each other.”
“Dmitri Mendeleev awakened from a dream that gave him the idea for the periodic table of elements - […].”
The underlined pronouns refer, respectively, to:
