On their own, men gossip, with no more than(1)per cent of conversaition time devoted to non-social subjects; while in mixed groups, the proportion of male conversation time devoted to "highbrow" subjects increases to between(2) and(3) per cent.（请填数字）

A. Orbital space around the star.
B. NASA discovered new habitable planets.
C. How Kepler spacecraft detects planets orbiting distance stars.
D. Why Earth and Mars are considered to be in the habitable zone .

A. Orbital space that is close to the star.
B. Orbital space that keeps the planet's surface neither too hot nor too cold.
C. Orbital space that is far from the star.
D. Orbital space that is around the sun.