The ratio of X and Y ages at present is 4:5. 

Then, the ratio 20 years ago will not be more than the ratio at present.

So, from the options 9:10 is not satifying => its ratio is 0.9 which is greater than presnt ratio of 0.8.

The Session layer of the OSI model offers three different modes of communication : Simplex, half duplex, and full duplex.

#include<stdio.h>
int main(){

    int a[10],i,n,m,c=0;

    printf("Enter the size of an array: ");
    scanf("%d",&n);

    printf("Enter the elements of the array: ");
    for(i=0;i<=n-1;i++){
         scanf("%d",&a[i]);
    }

    printf("Enter the number to be search: ");
    scanf("%d",&m);
    for(i=0;i<=n-1;i++){
         if(a[i]==m){
             c=1;
             break;
         }
    }
    if(c==0)
         printf("The number is not in the list");
    else
         printf("The number is found");

    return 0;
}

Sample output:
Enter the size of an array: 5
Enter the elements of the array: 4 6 8 0 3
Enter the number to be search: 0
The number is found

The words in each pair are antonyms of each other.

Hence, Firm : Flabby :: Piquant : Bland.