Two balls are floating at the sea surface. Their separation is $1.30\,\text{m}$. A wave propagates across the sea surface, making the balls oscillate vertically. The separation between a crest and the neighbouring trough of the wave is $0.90\,\text{m}$. What phase difference exists between the two balls?
- A$55^{\circ}$
- B$110^{\circ}$
- C$160^{\circ}$
- D$260^{\circ}$