Which lines are parallel?

blue and red only
green and red only
green, blue and red
none
This is a well known Zöllner illusion, first described in 1860. It may be caused by this impression of depth. The black lines are parallel, too!
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Very interesting!
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Answers by country

blue and red only
green and red only
green, blue and red
none
answers
flagSwitzerland
0%
3%
90%
6%
30
flagFrance
0%
5%
82%
11%
17
flagPakistan
0%
20%
80%
0%
15
flagAustria
3%
10%
76%
9%
55
flagSingapore
9%
6%
75%
9%
32
flagMalaysia
0%
11%
72%
16%
18
flagGermany
3%
8%
70%
16%
300
flagUnknown
7%
7%
70%
14%
27
flagthe Netherlands
3%
3%
69%
19%
26
flagAustralia
2%
11%
68%
16%
79
flagRepublic of Ireland
10%
5%
68%
15%
19
flagPoland
4%
8%
67%
18%
19992
flagthe United Kingdom
2%
10%
64%
20%
241
flagGreece
4%
8%
62%
25%
24
flagthe United Arab Emirates
14%
10%
60%
7%
28
flagthe United States
5%
8%
59%
24%
788
flagSouth Africa
5%
23%
58%
5%
17
flagIndia
8%
11%
53%
23%
321
flagthe Philippines
7%
7%
50%
30%
40
flagCanada
7%
11%
47%
31%
63