#include &lt;stdio.h&gt;    #include &lt;stdlib.h&gt;    #include &lt;ctype.h&gt;    int main &#40;&#41;    &#123;        char str&#91;&#93; = &quot;ffff&quot;;        long int number;        if &#40;isxdigit&#40;str&#91;0&#93;&#41;&#41;        &#123;            number = strtol &#40;str, NULL, 16&#41;;            printf &#40;&quot;%ld\n&quot;, number&#41;;        &#125;        return 0;    &#125;
A. 64345
B. 21312
C. 65535
D. Error
Answer:A
#include &lt;stdio.h&gt;    #include &lt;stdlib.h&gt;    #include &lt;ctype.h&gt;    int main &#40;&#41;    &#123;        char str&#91;&#93; = &quot;ffff&quot;;        long int number;        if &#40;isxdigit&#40;str&#91;0&#93;&#41;&#41;        &#123;            number = strtol &#40;str, NULL, 16&#41;;            printf &#40;&quot;%ld\n&quot;, number&#41;;        &#125;        return 0;    &#125;
A. 64345 B. 21312 C. 65535 D. Error
Explanation:In this program, We are converting the hexadecimal number to decimal number.