Consider the following pairs :
Objects in space Description
1. Cepheids Giant clouds of dust and gas in space
2. Nebulae Stars which brighten and dim periodically
3. Pulsars Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched?

1. Cepheids	Giant clouds of dust and gas in space
2. Nebulae	Stars which brighten and dim periodically
3. Pulsars	Neutron stars that are formed when massive stars run out of fuel and collapse

Only one

Only two

All three

None

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