Question

We saw a flack of sheep grazing in the fields

Answer 1

Answer:

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

Answer 2

Answer:

In the US, “a flock” is singular: “A flock of sheep is….” In the UK, “a flock” might be considered plural: “a flock are….”

When I was in school, these words were called “collective nouns.” There are many of them, and the US/UK split often applies. Here’s another example: “The team is….” (US) and “The team are….” (UK).