Let's summarize the general rules of contract formation:

If a contract lacks consideration, the contract is Blank $1$ Question $5.$

If one or both of the parties lack capacity to contract the contract is Blank $2$ Question $5.$

If the subject of the contract is illegal, the contract is Blank $3$ Question $5.$

If there is no consensus, the contract is Blank $4$ Question $5.$

If the contract is verbal, the contract is Blank $5$ Question $5,$ but may be unenforceable if there is a requirement that the contract be in writing $($i$.$e$.$ requirements under the Statue of Frauds$).$

If the contract was entered into under duress, the contract is Blank $6$ Question $5.$

If one of the parties was the subject of undue influence, the contract is Blank $7$ Question $5.$