The question asks which of the options is not a true fruit. A true fruit is a mature ovary of a flowering plant that contains seeds. Let`s examine each option:
Option 1: Apple. Apples are true fruits because they develop from the fertilized ovary of an apple flower and contain seeds. This option is not the answer.
Option 2: Date. Dates are also true fruits as they develop from the fertilized ovary of a date palm flower and contain seeds. This option is not the answer.
Option 3: Grape. Grapes are true fruits since they develop from the fertilized ovary of a grapevine flower and typically contain seeds. This option is not the answer.
Option 4: Plum. Plums are true fruits because they develop from the fertilized ovary of a plum tree flower and contain seeds. This option is not the answer.
Therefore, based on the definition of a true fruit, the correct answer is option 1, Apple.