The speed of an ant is $75\text{cm/sec}$. The ant travels in a day is:

Given the speed of the ant is $75\text{cm/sec}$.
Total number of seconds in $1\text{day}=24\times 60\times 60=86400\text{seconds}$.

Calculate total distance traveled in centimeters:

$$\text{Distance}=75\times 86400=6480000\text{cm/day}$$

Convert this distance into meters (since $1\text{meter}=100\text{cm}$):

$$\text{Distance in meters}=\frac{6480000}{100}=64800\text{m/day}$$

Hence, option A matches correctly.