Explanation:

There are 4 Boys B1,B2,B3&B4. And 3 Girls G1,G2,G3.
Now the boys can sit in the following way 
*B1 *   B2 *  B3 *  B4 *
the girls can sit in the * Places,which ensures that no two girls sit side by side.
now as we see, there  are  5 * s.
in these 5 Places, 3 Girls can be arranged in 5P3 Ways.and for each such arrangements, the boys can be arranged in 4! Ways.
hence the total  number of arrangements=5P3*4!=60*24=1440

Hence, option 1 is the correct answer.