PLEASE HELP... I ONLY HAVE ABOUT 10 MINS TO ANSWER THIS Which of these sentences from the selection is an opinion?

a
The Keep Calm poster that Manley discovered dates back to the start of World War II.
b
Two of the three posters were displayed in public at the start of the war in order to raise the morale of the British people
c
Manley’s copy has become a rarity
d
Today, interpretations of the slogan are often lighthearted, but it is important to remember the significance of the motto’s original intent.