Open WhatsApp
Go to the group chat
Tap the group name at the top
Scroll to the message you want to check
Long-press the message
Tap Info or Message Info
View the read receipts list there
Note that you cannot disable read receipts only for a WhatsApp group
WhatsApp read receipts can only be turned off for individual chats, not groups
To disable read receipts for personal chats, go to WhatsApp Settings
Tap Privacy
Turn off Read Receipts