Bonjour,
Réponse :
a. The whole world watched the handover ceremony.
The handover ceremony was watched by the whole world.
b. The guide showed us a few British landmarks.
A few British landmarks were shown to us by the guide.
We were shown ( by the guide ) a few British landmarks.
c. Britain and China offered a special status to Hong Kong.
A special status was offered to Hong Kong by Britain and China.
Hong Kong was offered a special status by Britain and China.
d. They will soon shape a new culture.
A new culture will soon be shaped (by them.)
==> ( l' adverbe de fréquence se placent entre 'will' et 'be' )
Explications :
PASSIF
BE ( au temps de la phrase active ) + participe passé