• Discovery of Viroids: In 1971, the Swiss-American plant pathologist Theodor O. Diener (T. O. Diener) discovered that the causal agent of Potato Spindle Tuber Disease (PSTD) was not a virus, but a novel subviral infectious entity.
• Nature of Viroids: Diener proved that the agent consisted exclusively of a tiny, circular, single-stranded non-protein-coding RNA molecule ($246-467\text{ nt}$) devoid of any protective protein coat, for which he coined the term 'viroid'.
• Other Scientists Listed:
• W. M. Stanley (1935): Crystallized Tobacco Mosaic Virus (TMV).
• F. C. Bawden & N. W. Pirie (1937): Demonstrated that TMV virions contain both protein and RNA.
• Conclusion: T. O. Diener reported that potato spindle tuber disease is caused by viroids (Option 4).

Correct option: (4) T.0. Diener

• Principle of Antisense Oligonucleotides: An antisense molecule is an oligonucleotide designed to be strictly complementary in sequence and antiparallel in polarity to a targeted sense mRNA or coding DNA sequence, inhibiting translation or transcription through hybrid formation.
• Sequence Pairing: For the target sequence $5'\text{-ATTAAGGC-}3'$:
• The complementary Watson-Crick base pairing gives: $A \rightarrow T$ (or $U$ in RNA), $T \rightarrow A$, $G \rightarrow C$, and $C \rightarrow G$.
• Matching base-by-base yields the antiparallel complementary strand: $3'\text{-TAATTCCG-}5'$ (or $5'\text{-TAATTCCG-}3'$ when presented in direct alignment as an antisense sequence in the question).
• Conclusion: TAATTCCG represents the designated antisense molecule (Option 4).

Correct option: (4) TAATTCCG

• Membrane Filter Sterilization (Cold Sterilization): In microbiological and phytopathological laboratory protocols, heat-labile liquids (such as antibiotic solutions, vitamins, growth regulators, and viral inocula) cannot be autoclaved.
• Standard Pore Size: They are sterilized by membrane filtration using cellulose acetate, nylon, or PES membrane filters with a standard nominal pore diameter of $0.22\,\mu\text{m}$ (commonly specified as $0.2\,\mu\text{m}$).
• Sterility Mechanism: A $0.2\,\mu\text{m}$ pore size physically excludes all vegetative bacterial cells (Brevundimonas diminuta is used as the standard validation challenge), fungi, and mycoplasmas while permitting aqueous solutions to pass through.
• Conclusion: Filters of $0.2\,\mu\text{m}$ pore size are normally used (Option 3).

Correct option: (3) 0.2 um