Petrol problems

A little girl asks her mum, 'Mum, can I take the dog for a walk around the block?'   Her mum replies 'No, because she is in heat.'

'What does that mean?' asked the child.

'Go and ask your father. I think he's in the garage.'

The little girl goes out to the garage and says, 'Dad, can I take Lulu for a walk around the block? I asked Mum, but she said the dog was in the heat, and to come ask you.'

He took a rag, soaked it in petrol, and scrubbed the dog's backside with it to disguise the scent, and said 'Ok, you can go now, but keep Lulu on the leash and only go one time around the block.'

The little girl left and returned a few minutes later with no dog on the leash..

Surprised, Dad asked, 'Where's Lulu?'

The little girl said, 'She ran out of petrol about halfway round the block, so another dog is pushing her home.'