<p>Many companies <strong>regularly</strong> provide clients with updated information about their services via emails.</p>
<div>(A) regularly - This is the correct answer. The word "regularly" means consistently or at fixed intervals, indicating that the companies provide updated information on a regular basis.</div>
<div>(B) substantially - This is not the correct answer. The word "substantially" means significantly or considerably, which does not accurately describe how companies provide updated information.</div>
<div>(C) equally - This is not the correct answer. The word "equally" means in the same way or to the same degree, which does not accurately describe how companies provide updated information.</div>
<div>(D) perfectly - This is not the correct answer. The word "perfectly" means flawlessly or without any mistakes, which does not accurately describe how companies provide updated information.</div>