Which variable stars have pulsation periods between 1.5 hours and 1.2 days?
a. protostars
b. nebulas
c. rr lyrae variables
d. cepheid variables

C. RR Lyrae variables

RR Lyrae variables are variable stars that have pulsation periods of 1.5 hours to 1.2 days. 

Nebula is the cloud of interstellar dust and gas that forms a star. It is collborately shaped during colliding and collapsing of the interstellar mediums this is influenced by the gravitational attraction of the atoms and particles in the entites. Hence, there are three types of nebular namely, are classical nebula, diffuse nebula, planetary nebular and supernova remnants.

It's important for a woman to know she is pregnant within the first trimester so she won't consume any alcohol or cigarettes which will harm the baby.

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