The NEET 2021 exam on September 12 saw around 16 lakh candidates competing for MBBS and BDS seats. If you attempted the O4 paper from Series O, the official NEET 2021 O4 Answer Key helps you check your answers and estimate your score. This page provides a detailed table with all 200 questions and correct answers, making evaluation easy. Explore the O4 code for insights into your performance.
Details about the NEET 2021 O4 Answer Key
The NEET 2021 O4 answer key corresponds to the O4 paper from Series O, one of 24 unique question paper codes issued by NTA (covering Series M, N, O, and P, each with six codes). The O4 paper had 200 questions (180 to be attempted) in Physics, Chemistry, and Biology, totaling 720 marks.
It followed a format with Section A (35 questions) and Section B (15 questions, 10 to be attempted). The O4 answer key was released on September 15, 2021, with the final key published on October 1, alongside the results.
The O4 paper had a demanding Physics section, with about 45% of questions centered on nuclear physics and quantum mechanics—topics that required strong conceptual clarity. Chemistry was moderate, focusing on chemical equilibrium, while Biology was lengthy, requiring a deep understanding of human physiology.
Below is the complete NEET 2021 O4 Answer Key, listing all 200 questions and correct answers for easy comparison.
NEET 2021 O4 Answer Key PDF Download
Below, you’ll find all 200 questions and their correct answers in a table for easy reference.
Please download the NEET 2021 O4 Answer key PDF.
| Question No. | Answer |
|---|---|
| 1 | 4 |
| 2 | 2 |
| 3 | 1 |
| 4 | 1 |
| 5 | 2 |
| 6 | 1 |
| 7 | 4 |
| 8 | 1 |
| 9 | 4 |
| 10 | 1 |
| 11 | 2 |
| 12 | 1 |
| 13 | 2 |
| 14 | 4 |
| 15 | 4 |
| 16 | 2 |
| 17 | 3 |
| 18 | 4 |
| 19 | 4 |
| 20 | 4 |
| 21 | 3 |
| 22 | 4 |
| 23 | 3 |
| 24 | 1 |
| 25 | 2 |
| 26 | 2 |
| 27 | 4 |
| 28 | 3 |
| 29 | 2 |
| 30 | 3 |
| 31 | 4 |
| 32 | 1 |
| 33 | 4 |
| 34 | 2 |
| 35 | 3 |
| 36 | 3 |
| 37 | 2 |
| 38 | 2 |
| 39 | 2 |
| 40 | 4 |
| 41 | 1 |
| 42 | 3 |
| 43 | 2 |
| 44 | 3 |
| 45 | 2 |
| 46 | 2 |
| 47 | 4 |
| 48 | 3 |
| 49 | 2 |
| 50 | 4 |
| 51 | 4 |
| 52 | 3 |
| 53 | 3 |
| 54 | 1 |
| 55 | 4 |
| 56 | 2 |
| 57 | 3 |
| 58 | 4 |
| 59 | 2 |
| 60 | 1 |
| 61 | 4 |
| 62 | 4 |
| 63 | 3 |
| 64 | 4 |
| 65 | 3 |
| 66 | 3 |
| 67 | 2 |
| 68 | 1 |
| 69 | 1 |
| 70 | 3 |
| 71 | 1 |
| 72 | 4 |
| 73 | 4 |
| 74 | 1 |
| 75 | 2 |
| 76 | 2 |
| 77 | 3 |
| 78 | 3 |
| 79 | 1 |
| 80 | 2 |
| 81 | 2 |
| 82 | 3 |
| 83 | 3 |
| 84 | 3 |
| 85 | 4 |
| 86 | 3 |
| 87 | 4 |
| 88 | 1 |
| 89 | 2 |
| 90 | 1 |
| 91 | 1 |
| 92 | 1 |
| 93 | 1 |
| 94 | 3 |
| 95 | 1 |
| 96 | 1 |
| 97 | 2 |
| 98 | 2 |
| 99 | 2 |
| 100 | 4 |
| 101 | 3 |
| 102 | 1 |
| 103 | 3 |
| 104 | 3 |
| 105 | 1 |
| 106 | 1 |
| 107 | 3 |
| 108 | 1 |
| 109 | 3 |
| 110 | 2 |
| 111 | 2 |
| 112 | 2 |
| 113 | 1 |
| 114 | 1 |
| 115 | 4 |
| 116 | 2 |
| 117 | 4 |
| 118 | 3 |
| 119 | 1 |
| 120 | 1 |
| 121 | 3 |
| 122 | 4 |
| 123 | 4 |
| 124 | 4 |
| 125 | 1 |
| 126 | 2 |
| 127 | 4 |
| 128 | 1 |
| 129 | 4 |
| 130 | 3 |
| 131 | 3 |
| 132 | 3 |
| 133 | 1 |
| 134 | 4 |
| 135 | 4 |
| 136 | 2 |
| 137 | 1 |
| 138 | 4 |
| 139 | 3 |
| 140 | 2 |
| 141 | 3 |
| 142 | 4 |
| 143 | 3 |
| 144 | 1 |
| 145 | 1 |
| 146 | 4 |
| 147 | 1 |
| 148 | 4 |
| 149 | 3 |
| 150 | 4 |
| 151 | 1 |
| 152 | 2 |
| 153 | 1 |
| 154 | 1 |
| 155 | 4 |
| 156 | 4 |
| 157 | 4 |
| 158 | 2 |
| 159 | 3 |
| 160 | 1 |
| 161 | 1 |
| 162 | 3 |
| 163 | 2 |
| 164 | 3 |
| 165 | 2 |
| 166 | 4 |
| 167 | 4 |
| 168 | 1 |
| 169 | 4 |
| 170 | 3 |
| 171 | 1 |
| 172 | 3 |
| 173 | 1 |
| 174 | 1 |
| 175 | 1 |
| 176 | 3 |
| 177 | 1 |
| 178 | 4 |
| 179 | 1 |
| 180 | 2 |
| 181 | 2 |
| 182 | 2 |
| 183 | 3 |
| 184 | 1 |
| 185 | 3 |
| 186 | 1 |
| 187 | 4 |
| 188 | 4 |
| 189 | 3 |
| 190 | 4 |
| 191 | 1 |
| 192 | 4 |
| 193 | 3 |
| 194 | 2 |
| 195 | 3 |
| 196 | 2 |
| 197 | 3 |
| 198 | 3 |
| 199 | 2 |
| 200 | 3 |
To explore other answer keys from Series S, check out the NEET 2021 O2 Answer Key, NEET 2021 O3 Answer Key, NEET 2021 O1 Answer Key, NEET 2021 O5 Answer Key, and NEET 2021 O6 Answer Key, For a full list of all 24 codes, visit the NEET 2021 Answer Key pillar page.
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