What is the subnet mask of /22?

The subnet mask for a /22 CIDR notation is **255.255.252.0**.

In binary, a /22 subnet mask would look like this:
```
11111111.11111111.11111100.00000000
```
Which translates to decimal as:
```
255 255 252 0
```

So the correct answer from your choices is **255.255.252.0**.