mount up vs grow up

5 years ago

 
Hello, everyone!
What is the difference between 'mount up' and 'grow up'?
"It took around seven years and 210,000 matchsticks to complete the grandmother clock. It now has pride of place in our living room, and chimes to the tune of Big Ben every 15 minutes.  As the pieces (30) ________ up, the space in our house disappeared. “We’re going to have to find new homes for some of your models,” I said to Brian one day."
#30
A grew
B formed
C mounted
D ascended
SOURCE: https://zno.osvita.ua/english/all/160