None of the answers.
It is ultimately safer to leave pets at home, with shade (or air conditioning) and fresh, cool water.

Heat can build up in cars even on moderately warm days, even when parked in the shade, even with the windows cracked. Windows open all of the way can lead to pets jumping out, getting lost or hit by passing cars. Added to this, some pets get very stressed being left alone, watching their owners leave. Older pets, pets on some medications, pets with heart conditions, and short-nosed pets are more at risk for heat and stress related events.

Summer Fun - Summer Safety
Weather-related links

Additional Information about Car Safety
Pets in Parked Cars can be a Deadly Mistake
Canine.com
Don't Leave Your Pet in a Parked Car
Humane Society of the United States
Leaving Your Pet in a Parked Car Can Be a Deadly Mistake
The Peoria Humane Society

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