Roots grow in length and width from primary and secondary meristem.
Growth in girth is caused by other meristems, called secondary meristems.
Roots grow in length and girth caused by meristems.
What grow in length and girth caused by meristems?

1) roots
2) ferns
3) legumes
4) Trees
5) plants
6) Flowers
7) bushes
8) bamboo