The correct option is C n−2
Given, a3−a2a2+a4−a2a3+a5−a2a4+............+an−a2an−1
Since, an=a+(n−1)d
∴a2=a+d,a3=a+2d,a4=a+3d.............. and an−1=a+(n−2)d
Substitute the values of a2,a3,a4,a5,............,an−1,an in given statement. we get,
a+2d−(a+d)a+d+a+3d−(a+d)a+2d+a+4d−(a+d)a+3d+............+a+(n−1)d−(a+d)a+(n−2)d
⇒da+d+2da+2d+3da+3d+............+(n−2)da+(n−2)d
given, a=0
⇒dd+2d2d+3d3d+............+(n−2)d(n−2)d
⇒1+1+1+........(n−2)times=n−2
∴ Option C is correct.