Can you explain this sentence error?

[J.Shi]

<p>Contrasting with most other 15th century rulers, Portuguese kings could count on the support of the aristocracy in any overseas ventures. </p>

<p>The choices are:</p>

<p>A. Contrasting with
B. most other
C. could count on
D. in any</p>

<p>The answer is A. Can anyone explain why?</p>

[Martha]

<p>"In contrast to"</p>