In order to keep fit (A)/, Joyce exercised vigorously(B)/ in the mornings,…

Explanation:

The sentence is awkward because the place, frequency and time phrases are misordered and punctuated in the segment "in the mornings, thrice a week, at the gym." The clearer and more natural phrasing places the place right after the verb, followed by frequency and then time of day.

Corrected sentence: In order to keep fit, Joyce exercised vigorously at the gym three times a week in the mornings.

• What was wrong: The original segment "in the mornings, thrice a week, at the gym" mixes place and time phrases in an awkward order and uses commas that make the sequence unclear.

• How to fix it: Put the place after the verb ("at the gym"), then give the frequency ("three times a week"), then the time of day ("in the mornings").

• Style note: "three times a week" is generally more natural in modern usage than "thrice a week."