C# solution
\nStringBuilder sb = new StringBuilder();\n        sb.Append(s);\n        for(int i=0;i<sb.Length;i++){\n            if(s[i]==\'?\'){\n                for(char 
```\nStringBuilder sb = new StringBuilder();\n        sb.Append(s);\n        for(int i=0;i<sb.Length;i++){\n            if(s[i]==\'?\'){\n                for(char j=\'a\'; j<=\'z\';j++){\n                    if(i-1>=0 && j == sb[i-1]) continue;\n                    if(i+1<sb.Length && j == sb[i+1]) continue;\n                    sb[i] = j;\n                }\n            }\n        }\n        return sb.ToString();\n```
['String']