Walked is the verb in the sentence
A) submitted would be correct
The third excerpt is structured correctly.
The answer is D
Tû’s descendants became the Mâori, the humans who are able to master anything that they decide to conquer.
Exercise 1:
an ocean
a pebble
an insect
a bug
a web
an archaeologist
an eagle
a geologist
a fossil
an ancient fossil
You only change "a" to "an" when the next word starts with a vowel.