They come out at night without being called and are lost in the day without…

Concept: In this style of riddle, each clue is a literal description of a naturally recurring phenomenon, phrased without naming it directly. To solve it, decode each clue into a real-world characteristic — when does it appear, and is its appearance or disappearance caused by an outside agent, or is it simply a natural cycle? — and find the option whose everyday behaviour matches every clue simultaneously.

Applying it here: Two clues are given: they come out at night without being called, and they are lost in the day without being stolen. Something that is visible at night and invisible during the day purely because of a natural cycle — not because an agent brings it or removes it — fits Stars: stars are always present in the sky but only visible against darkness, and sunlight during the day naturally washes them out of view, matching “lost in the day without being stolen” exactly.

Why the other options don't fit:

• Flights: they depart and arrive on schedules set by an airline, so their presence or absence is controlled by human scheduling, not by the day-night cycle. They do not appear only at night, nor vanish specifically at daybreak.

• Bats: although bats are nocturnal, they hide by roosting during the day rather than being “lost”. Their disappearance is their own action, not a natural, agent-free cause, so the riddle's phrasing does not fit.

• Light: daylight itself is present during the day, not lost then — the opposite of what the riddle describes.

Conclusion: Only Stars satisfy both the nighttime appearance and the daytime disappearance as a natural, agent-free cycle, so Stars is the correct answer.