Geijer's comment supports MacGregor's point in that it illustrates the popularity of tea in Britain during the 1800s.
Geijer said that in the 1800s, the British public fell so in love with tea that it became the national drink.
This supports MacGregor's point about the love in Britain for tea such that this love has continued to the current period.
In conclusion, option C is correct.
Find out more on Britain and tea at https://brainly.com/question/25757128.