To solve this problem, we need to analyze each statement regarding plant anatomy and physiology:$\newline \bullet$A. Lenticels are the lens-shaped openings permitting the exchange of gases.$\newline$ - Lenticels are indeed small, lens-shaped openings in the bark of woody plants that allow for gas exchange.$\newline$ - Therefore, statement A is correct.$\newline \bullet$B. Bark formed early in the season is called hard bark.$\newline$ - Bark formed early in the season is typically called "soft bark" or "early bark," not "hard bark."$\newline$ - Therefore, statement B is incorrect.$\newline \bullet$C. Bark is a technical term that refers to all tissues exterior to vascular cambium.$\newline$ - Bark includes all tissues outside the vascular cambium, which consists of the secondary phloem, periderm, and any remaining primary tissues.$\newline$ - Therefore, statement C is correct.$\newline \bullet$D. Bark refers to periderm and secondary phloem.$\newline$ - Bark indeed includes both the periderm (which replaces the epidermis in mature stems) and the secondary phloem.$\newline$ - Therefore, statement D is correct.$\newline \bullet$E. Phellogen is single-layered in thickness.$\newline$ - Phellogen, also known as cork cambium, is typically a single layer of meristematic cells that produces cork cells.$\newline$ - Therefore, statement E is correct.$\newline$Now, let's identify the correct statements:$\newline$A and D are correct.$\newline$This corresponds to Option 2: A and D only.