1. Could not

Encyclopedia: Couldn't

• uncertainly
• uncertainness
• uncertainty
• uncertainty principle
• uncertified
• unchain
• unchained
• unchallengeable
• unchallenged
• unchangeability
• unchangeable
• unchangeableness
• unchangeably
• unchanged
• unchanging
• unchangingness
• unchaperoned
• uncharacteristic
• uncharacteristically
• uncharged
• uncharitable
• uncharitably
• uncharted
• unchartered
• unchaste