Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours. The most likely explanation is that:________.1. The star is cepheid variable.2. The star is a member of binary eclipsing star system.3. The star is peridically ejecting gas into space every 73 hours.4. The star is a white dwarf.