Before a problem can be solved, it must be obvious ________ the problem itself is.[ ]

The disco music，digitally________in the studio，sounded fantastic at the party that night

How much do you have in your pocket?—150 yuan, all of _______ came from my grandma.

It_____ have been Tom that parked the car here, as he is the only one with a car.

The advertisement says the vacuum cleaner (吸尘器) can ______ everything from the floor. Do you believe it?