When walter devotes attention and practice to completing tax returns, and has gained experience in that area, he is demonstrating?

He is demonstrating "expertise".

Explanation:

When you have special skills in any field and you get that by working hard and paying attention to your work, then you are demonstrating expertise. We achieve expertise by doing lot of work, attention and care. if you have goals to become expert in your field, one day you will get expertise.

answer; i believe the correct answer is (crops);

in 342 bc j._c. egypt fell into the hands of the persians, under the reign of nectanebo ii

greek city-states unite in a revolt against the persian empire at the beginning of the fifth century bc. j.-c  

from the year 660 or 659 bc ad, cyrus preached the revolt against the medes to deliver the persians.