Read the information and examples in the box. Then answer the questions.

You can use participle clauses after nouns to help you describe a scene.

I saw atoms dancing before my eyes.

A participle clause is similar to a relative clause:

I saw atoms which were dancing before my eyes.

Here are more examples from the radio programme:

$1$ I saw a pale student kneeling beside the monster he had put together.

$2$ There was a red screen formed by flowing blood.

$3$ I could see long rows of atoms twisting like a snake.

$4$ Benzene molecules, like the snake made of atoms, have the shape of a ring.

$1$ Which clauses in $1-4$ are made with:

a present participles $(-$ing$)?$

$2$ Which kind of participle has:

b past participles $($often$-$ed$)?$

a an active meaning?

b a passive meaning?