Find the Pattern in Symbols and Answer. What must be the answer and Why

Try to find the solution. Which option or Block would fit in the Blank space and Why? What pattern do You observe in this Puzzle.

• Just want to be absolutely sure, the bottom right one is a triangle, right? It looked just a little too rounded for me to not check. – ColdFrog Feb 6 '18 at 19:55
• Yes, It is A Triangle. – RJ100706 Feb 6 '18 at 20:25

The block that fits the blank space best is

the fourth one

And the pattern observed is

Each row and column contains only 2 identical symbols

Here's an ascii drawing:
$\begin{array}{ccccc}\\▲&◆&?&?&←\\→&▲&⬟&?&→\\⬟&◆&→&⬟&←\\\rm O&←&■&\rm O&⬟\\▲&→&■&◆&▲\end{array}$

The only one that fits is
$\begin{array}{cc}\\◆&■\\&\rm O\end{array}$
Because it gives row 1 two ◆ and column 4 two O.

Proof the others don't work:

The first block would put two ⬟ in row 2, and there are already two →
The second block would put two → in column 3, and there are already two ■
The third block would put two ⬟ in column 3, and there are already two ■
The fifth block doesn't give row one two of anything.

I posted this some time ago, but the I found a flaw in it, so I deleted. However, it migt help somebody else, so I decided to undelete it.

Let's look at:

How many times each symbol appear two times in the same row or column?

So, let's analyze that:

1st column: Two triangles
2nd column: Two diamonds
3rd column: Two squares
4th column: ???
5th column: Two left arrows

1st row: ???
2nd row: Two right arrows
3rd row: Two pentagons
4th row: Two circles
5th row: Two triangles

Now, what can't fill the spaces while mantaining this pattern?

The 3rd and the 5th pictures won't produce any repeating symbol in the 1st row.
The 1st picture would make the 2nd row with two pairs of repeating symbols.
The 2nd picture would make the 3rd column with two pairs of repeating symbols.

This leaves us with only a single possibility:

The solution is the 4th picture.

This fills the patterns with:

4th column: Two circles
1st row: Two diamonds

• This looks like the same conclusion I came to; however, what's wrong with the 4th picture? It doesn't need to produce any repeating combinations because row 2 already has a repeating combination – Tas Feb 7 '18 at 21:19
• @Tas That is what happens when people interrupts me many times for no good reason when I'm are trying to solve a puzzle, I end commiting silly mistakes. My bad. Now, although I got very close, you completed it first. – Victor Stafusa Feb 7 '18 at 21:25
• Truthfully I had the same problem. I found the answer, then when I was writing it all out I got confused and initially thought 1 was meant to be it and couldn't remember why I had discounted it, but eventually noticed the flaw with it again – Tas Feb 7 '18 at 21:29