I need solve this MCQ questions

QUESTION 10 Any agreement between a trade union and an employer would only be considered a contract if it is written and signed. ( ) True O False QUESTION 11 When surrounding facts and circumstances indicate that an agreement exists, this is called? a. Collective agreements O b. Implied contracts O c. Express contracts O d. Enforceable contracts QUESTION 12 The bids made during an auction are considered an invitation to treat. ( ) True False QUESTION 13 Common mistake generally makes a contract: O a. Void O b. Valid O c. Voidable Od. Enforceable QUESTION 14 When the offeree says that he accepts the offer under certain conditions that is considered a rejection of the offer. ( ) True OFalse QUESTION 15 An agreement between a trade union and an employer is not considered a contract if it is unwritten. ( ) True OFalse QUESTION 16 Collective agreements are not legally enforceable unless they are in writing. ( ) True False QUESTION 17 Which of the following is not an essential element of all types of contracts? O a. Capacity O b. Agreement O c. Legality O d. Writing