Which of the following is a day-neutral plant?

$A$ hypothetical 'florigen' could be produced prematurely in a long-day plant by exposing it to:

The pigment involved in red-far red light interconversion is

There are many plants that do not show any correlation between exposure to light duration and the induction of flowering. Such plants are called $..........$.

When all parts except the leaves of a short-day plant are covered with a light-proof cover and then subjected to short-day light/dark treatment,it will produce flower buds. When a portion of this plant is grafted onto another plant of the same species which has been prevented from flowering by excessive exposure to light,this latter plant will also produce flower buds. Which is the best inference from this result?

Which of the following is/are example/s of long day plant?
$I.$ Tomato
$II.$ Maize
$III.$ Rice
$IV.$ Radish
Choose the correct option accordingly.