Identify the figure given in the options which when put in place of ‘?’ will logically complete the series.

Correct — C.

Rule: one triangle and one plus sign are added at every step, and each element fills its own edge before spilling onto a new one.

Frame 1: 1 triangle on the left edge, 1 plus.
Frame 2: 2 and 2. Frame 3: 3 and 3.

The left edge takes only three triangles. So in frame 4 the fourth triangle hangs below the bottom edge pointing down, while the four plus signs still fit in their single column.

The missing frame therefore needs 5 triangles — three on the left edge, two below the bottom edge — and 5 plus signs, four down the column and the fifth beside the lowest of them.

That is option (c).

Why the others are wrong

• (a)
  Both counts stall at four. Option (a) shows three triangles on the left, one below the bottom edge and four plus signs — frame 4's totals exactly, with the fourth plus merely relocated to the top right.
• (b)
  Five triangles but only four plus signs. Option (b) grows the triangles correctly and leaves the plus count where frame 4 had it, so the two elements stop advancing together.
• (d)
  Frame 4 unchanged. Option (d) repeats three left-hand triangles, one triangle below the bottom edge and four plus signs; nothing has been added at all.

This is an additive series with a capacity limit. Both elements grow by one each step, but each has a fixed number of places on its own side of the square.

Once a side is full the next element does not squeeze in — it starts on the next side, keeping the same outward orientation. That is why the fourth triangle appears below the square rather than on its left.

So answer in two passes: count the elements to reach the totals the frame needs, then check that they have been placed on the right edges and are pointing the right way.

Key facts

• Both elements grow by exactly one per step: 1, 2, 3, 4 across the given frames, so the answer carries 5.
• The left edge holds at most three triangles, after which they hang below the bottom edge pointing outward.
• The plus signs fill one column from the top down, and the fifth begins a second position beside the lowest.

Common traps

• Checking the triangles, finding them right, and assuming the plus signs match.
• Expecting the extra triangle to squeeze onto the left edge instead of moving to a new edge.
• Choosing the option that simply repeats the fourth frame.

No directly related past PYQ was found.