Past Perfect, Past Perfect Continuous or Past Simple? – Past mix

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I ……………………..(work) for the company for three months before I ……………….(realize) my neighbour also worked there.
As soon as George …………………..(finish) the race, he …………………(drink) 3 glasses of water.
Everything …………………(be) white because it ……………………(snow) all night.
My parents …………….(be) really happy when I …………………(qualify) because they ……………………..(always want) me to be a doctor.
She ………………..(be) exhausted when she …………………..(get out) of the pool because she ……………………… (swim) 3 kilometers.
We ……………………….(only sit) down when the waitress ………………….(come) to take our order.
I could tell from their faces that they ……………………….(argue) about something.
Our dinner ………………… (not be) ready because I ………………..(forget) to switch the oven on.
By the time the doctor …………………(arrive), the baby …………………..(be born).
After John ………………….(finish) his dinner he………………….. (go) straight to bed.

I had worked/had been working for the company for three months before I realised my neighbour also worked there.
As soon as George had finished the race, he drank 3 glasses of water.
Everything was white because it had snowed/had been snowing all night.
My parents were really happy when I qualified because they had always wanted me to be a doctor.
She was exhausted when she got out of the pool because she had swum 3 kilometers.
We had only sat down when the waitress came to take our order.
I could tell from their faces that they had argued/had been arguing about something.
Our dinner wasn’t ready because I had forgotten to switch the oven on.
By the time the doctor arrived, the baby had been born.
After John had finished his dinner he went straight to bed.