Select the option that represents the letters that, when placed from left to right in the blanks below, will complete the letter-series.
a_mx_q_yc_o_

Let's observe the series structure by examining alternating positions or shifting differences between elements.
The series text is: a _ m x _ q _ y c _ o _

Let's look at the letters at alternate odd positions:

a→m→_→c→o
a(1)
+12

​
m(13)
+12

​
y(25)
+4

​
c(3) ? Let's check another gap pattern.

What if we group them into sets of pairs or triplets?
Let's analyze the options:
If we plug in p, b, n, r, z (Option B):
a [p] m x [b] q [n] y c [r] o [z]

Let's check the difference between consecutive letters:

a(1)→p(16)⟹+15

p(16)→m(13)⟹−3

m(13)→x(24)⟹+11
Let's see if there is an alternating series of two or three interleaved sub-sequences:

Let's separate into 3 sub-series (indices 1, 4, 7, 10; 2, 5, 8, 11; 3, 6, 9, 12):

a,x,_,_

_,_,y,o

m,q,c,_

Let's try 2 sub-series (odd and even positions):

Odd positions: 1,3,5,7,9,11⟹a, m, _, _, c, o

a(1)
+12

​
m(13)
+12

​
y(25)
+4

​
c(3)?
Let's look at the options instead:
Notice the options have common letters like p, b, n, r, z.
If the string is: a [p] m x [b] q [n] y c [r] o [z]
Let's look at pairs:
(a, p),(m, x),(b, q),(n, y),(c, r),(o, z)
Let's check the positional difference within each pair:

p(16)−a(1)=15

x(24)−m(13)=11

q(17)−b(2)=15

y(25)−n(14)=11

r(18)−c(3)=15

z(26)−o(15)=11

Wow! The pattern is perfectly consistent: The pairs alternate between having a difference of +15 and +11.

Pair 1: a→p (+15)

Pair 2: m→x (+11)

Pair 3: b→q (+15)

Pair 4: n→y (+11)

Pair 5: c→r (+15)

Pair 6: o→z (+11)

Thus, the letters to fill the blanks are exactly p, b, n, r, z.