Question

ᴍᴀᴋᴇ ᴛʜᴇ ꜱᴇɴᴛᴇɴᴄᴇ ᴜꜱɪɴɢ ɪᴅɪᴏᴍꜱ 1.ꜱᴛᴜᴍʙʟᴇ ᴏɴ​

Answer 1

They stumbled on a bizzare plot.

Answer 2

Answer:

1.unexpectedly I stumbled across/on/upon this book by chance. We stumbled onto/across the ruins of an old fort.

2.They stumbled on/upon a bizarre plot. He stumbled onto the truth.

Hope It Helps!!!

Explanation:

actually stumble on is a idiom  which shows tripping on something ...