Two sources are said to be coherent if they produce waves

$n$ incoherent sources, each emitting beams of intensity $I_0$, are superimposed at a point. The resultant intensity at the point is:

Two waves coming from two coherent sources,having different intensities,interfere. The ratio of their maximum intensity to the minimum intensity is $25$. What is the ratio of the intensities of the sources?

Which phenomena can be explained by the wave nature of light?

Two sources $S_1$ and $S_2$ emit waves of wavelength $\lambda$. For destructive interference at point $P$,the path difference $(S_1P - S_2P)$ must be:

Consider the following statements about interference of light.
$A$-When crest of one wave coincides with crest of another wave at a point,this point is a point of destructive interference.
$B$-Two coherent sources emit waves of the same frequency with a constant phase difference.
Choose the correct option from the following.