A cash book is not mandatory for all businesses. However, it is highly recommended for businesses to keep a cash book to accurately record all cash transactions. This helps in maintaining proper financial records, tracking cash flow, and monitoring expenses and revenues. Additionally, a cash book can also be useful for budgeting, forecasting, and preparing financial statements. **

Online teaching may be mandatory in certain situations, such as during a public health crisis when in-person instruction is not possible. However, in general, the decision to teach online is typically made by educational institutions or individual educators based on their specific circumstances and needs. Some institutions may require a certain percentage of courses to be offered online, while others may leave it up to the discretion of the instructor. Ultimately, the requirement for online teaching depends on the policies and guidelines of the specific educational institution. **

In poker, to bluff means to make a bet or raise with a weak hand in order to deceive opponents into thinking you have a strong hand. The goal of bluffing is to get your opponents to fold their better hands, allowing you to win the pot without having the best cards. Bluffing is a strategic element of the game that requires reading your opponents and understanding the dynamics of the game. Successful bluffing can be a powerful tool in a player's arsenal, but it also carries the risk of being called and losing the pot. **

No, Nintendo Switch Online is not absolutely mandatory to enjoy playing games on the Nintendo Switch. While subscribing to Nintendo Switch Online provides access to online multiplayer features, cloud saves, and a selection of classic NES and SNES games, many games can still be played offline without a subscription. However, some games do require a Nintendo Switch Online subscription to access their online multiplayer modes. Ultimately, the decision to subscribe to Nintendo Switch Online depends on how important online multiplayer and the other features are to the individual player. **

A camera is not mandatory for online classes, but it can be helpful for certain activities such as virtual meetings, presentations, or group discussions where video communication is important. Some instructors may require students to have a camera for participation or engagement purposes, but in general, it is not a strict requirement. Students can still actively participate in online classes using just audio or text communication if they do not have a camera. **

A camera is not mandatory during online classes, but it can be helpful for engagement and participation. Some instructors may request that students have their cameras on to create a more interactive and engaging learning environment. However, there may be valid reasons for students to not have their cameras on, such as privacy concerns or technical limitations. Ultimately, it depends on the specific requirements and expectations set by the instructor or educational institution. **

It is not mandatory to select an airplane seat online. Many airlines offer the option to select a seat during the online check-in process, but it is not required. Passengers can also choose their seat at the airport check-in counter or have a seat assigned to them at the gate. However, selecting a seat online can provide more options and ensure that passengers get their preferred seat. **

It is difficult to determine if the poker tournament was fair without more specific information about the tournament. Factors such as the rules, structure, and organization of the tournament, as well as the conduct of the players and organizers, would all need to be considered in order to make a fair assessment. Without this information, it is not possible to definitively say whether the tournament was fair or not. **