Answer: Option B. -> Convert floating-point number to a string

The gcvt() function CONVERT a floating-point number to a string. It converts given value to
a null-terminated string.

#include <stdlib.h>
#include<stdio.h>
int main(void)
{
char str[25];
double num;
int sig = 5; /* significant digits */
/* a regular number */
num = 9.876;
gcvt(num, sig, str);
printf("string = %s\n", str);
/* a negative number */
num = -123.4567;
gcvt(num, sig, str);
printf("string = %s\n", str);
/* scientific notation */
num = 0.678e5;
gcvt(num, sig, str);
printf("string = %s\n", str);
return(0);
}

Output:
string = 9.876
string = -123.46
string = 67800

Answer: Option B. -> Got it

memcmp compares the first 2 bytes of the blocks dest and src as unsigned chars. So, 

the ASCII value of 97 is 'a'.

if((i = memcmp(dest, src, 2))==0) When comparing the array dest and src as unsigned 

chars, the first 2 bytes are same in both variables.so memcmp returns '0'.
Then, the if(0=0) condition is satisfied. Hence the output is "Got it".

Answer: Option C. -> 65, 66.666000

Function atoi() CONVERTS  the string to integer. 

Function atof() converts the string to float.

result1 = result1+atoi(i); 
Here result1 = 10 + atoi(55.555); 
result1 = 10 + 55; 
result1 = 65;

result2 = result2+atof(i); 
Here result2 = 11.111 + atof(55.555); 
result2 = 11.111 + 55.555000; 
result2 = 66.666000; 
So the output is "65, 66.666000" .

Answer: Option C. -> b

The ungetc() function pushes the character c back onto the named input stream, which must

 be open for reading.

This character will be returned on the next call to getc or fread for that stream.

One character can be pushed back in all situations.

A second call to ungetc without a call to getc will force the previous character to be forgotten.

Answer: Option B. -> 2

scanf() returns the number of variables to which you are provding the input.

i = scanf("%d %d", &i, &i); Here Scanf() returns 2. So i = 2.

printf("%d`setminus`n", i); Here it prints 2.

Answer: Option C. -> 2.000000, 0

Both ceil() and floor() return the integer found as a double.

floor(2.5) returns the largest integral value(round down) that is not greater than 2.5. So output is 2.000000.

ceil(2.5) returns 3, while converting the double to int it returns '0'. 
So, the output is '2.000000, 0'.

Answer: Option C. -> 2.000000, 0

Answer: Option B

Explanation:

In the program, printf() returns the number of charecters printed on the console

i = printf("How r u`setminus`n"); This line prints "How r u" with a new line character and returns the length of string printed then assign it to variable i. 
So i = 8 (length of 'n' is 1).

i = printf("%d`setminus`n", i); In the previous step the value of i is 8. So it prints "8" with a new line character and returns the length of string printed then assign it to variable i. So i = 2 (length of '`setminus`n' is 1).

printf("%d`setminus`n", i); In the previous step the value of i is 2. So it prints "2".

Answer: Option C. -> returns a random number generator with a random value based on time.

The randomize() function initializes the random number generator with a random value based on time. You can try the sample program given below in Turbo-C, it may not work as expected in other compilers.

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
int main(void)
{
randomize();
printf("Random number in the 0-99 range: %d\n", random (100));
return 0;
}

Answer: Option A. -> Yes

Do like this fprintf(stdout, "%s %d %f", str, i, a);

Answer: Option A. -> flushes all streams and specified streams.

"fflush()" flush any buffered output associated with filename, which is either a file opened 

for writing or a shell command for redirecting output to a pipe or coprocess.

Example: 
fflush(FilePointer);
fflush(NULL); flushes all streams.