$18.$Many applications such as banking services use relational database management systems $($RDMS$)$to process user data, RDMS fulfill the ACDD properties. Which one of the following statements about relational databases is wrong?

A$.$Atomicity property guarantees that each transaction is treated as a single operation.

B$.$Entity$-$Relation models contain two major elements: entity and relationship.

C$.$RDMS use locks to ensure that at any time only one user changes the data.

D$.$Consistency property ensures that the data is in a consistent state all the time.

There is a fake coin in a pile of N coins, whereas a fake one has a lighter weight. There are two possible ways to identify the fake coin: sequential search or divide$-$and$-$conquer. Which one of the following statements is wrong?

A$.$The time complexity of the divide$-$and$-$conquer is O$($logN$).$

B$.$The time complexity of the sequential search is O$($N$).$

C$.$The best case of sequential search takes $1$comparison$.$

D$.$The best case of divide$-$and$-$conquer takes $1$comparison$.$