18. Focal length is a length which lies between
a. lens and object
b. lens and image
c. lens and second focus
d. lens and focal point
![18 Focal length is a length which lies between a lens and object b lens and image c lens and second focus d lens and focal point class=](https://us-static.z-dn.net/files/d93/f699ae4adf4e939e92f0be7d1bfd4631.jpg)