What code should be placed in Jasmine's shopping app to increment the cartTotal variable when clicking the "addItemButton"?

The correct choice for incrementing the cartTotal variable when the "addItemButton" is clicked is to use the assignment statement that updates the value of cartTotal by adding 1 to its current value. This is achieved by writing cartTotal = cartTotal + 1;.

In this statement, you are taking the existing value of cartTotal, adding 1 to it, and then storing that new value back into the cartTotal variable. This effectively updates the total to reflect the addition of a new item each time the button is clicked.

The other options do not correctly achieve the desired increment. For instance, setting cart total = 1; incorrectly initializes the variable to 1 without incrementing the total, while cartTotal + 1; simply calculates the new value without storing it or updating cartTotal. Lastly, the declaration of var cartTotal = cartTotal + 1; mistakenly attempts to re-declare the variable and would not properly increment it in the context of an existing variable. Thus, option C is the correct choice as it effectively increments the cartTotal variable as intended.