Which of the following mechanisms restricts gene expression (i.e. transcription) to only one of the two copies in a diploid organism ?

The next six (6) questions use the Adventure database shown below and sample data appropriately dispersed throughout the questions. For each question you have to select a single best answer.

The window function in the SQL code does which of the following?

Which of the following completes the CREATE TABLE statement for the Trade table? CREATE TABLE Trade (   TradeNo CHAR(4),   CustNo  _______,   EmpNo   _______,   AssetNo CHAR(2) NOT NULL,   Qty     INTEGER,   Price   DOUBLE,   TDate   DATE NOT NULL   Type    VARCHAR(10) NOT NULL,   Status  VARCHAR(10) NOT NULL,   CONSTRAINT PKTrade PRIMARY KEY (TradeNo)   CONSTRAINT FKCustomer FOREIGN KEY (CustNo) REFERENCES Customer (CustNo)   CONSTRAINT FKAsset FOREIGN KEY (AssetNo) REFERENCES _____ (AssetNo)   CONSTRAINT FKEmployee FOREIGN KEY (____) REFERENCES Employee (____))

Which of the following queries will show customer names and the number of bookings for customers with at least 2 bookings?    

The foreign key(s) that can accept null values without violating referential integrity is (are)

The data model shown below, and repeated in each of the remaining questions, describes “Adventure Services, LLC”, a business of taking customers on adventure tours and/or renting the necessary gear (biking, hiking, kayaking) for self-guided tours. Note that both the tours (services) and the necessary gear are considered to be the “products” in this business.

Which of the following queries of the Rental database will produce a non-repeating list of customer names, addresses, and phone numbers for the customers born in the 1980s who rented a vehicle before July 22, 2026?    

Null values in the column Booking.GuideID represent

The major components of the 3-schema DBMS architecture are which one of the following?