The combination of all INCORRECT statements is (1) A and D only.
Statements B and C are correct.

Statement-by-statement analysis

A. “Transformation frequency is influenced only by Agrobacterium genes, not by host plant genes.” – Incorrect

Plant transformation efficiency depends on both bacterial and host factors.

• Host genes affect susceptibility, T‑DNA transport, nuclear import and integration, and defense responses.​

• Therefore it is wrong to say transformation is influenced “only” by Agrobacterium genes.

B. “Single‑copy transgenic plants are preferred over multi‑copy plants for analysis.” – Correct

For genetics and stable expression studies, single‑copy inserts are usually favored because:

• Multi‑copy arrays are more prone to gene silencing and complex segregation, while single‑copy events are easier to map and analyze.​
  So B is a correct statement.

C. “Super virulent Agrobacterium strains can be generated by increasing vir gene copy number.” – Correct

“Super‑Agrobacterium” strains have been made by overexpressing vir genes (e.g., additional virG, virE, virD copies), which increases T‑DNA transfer and transformation frequency.​
So C is also correct.

D. “A non‑conditional negative selection marker must necessarily be driven by a strong constitutive promoter.” – Incorrect

Negative selection markers need sufficient expression under specific selective conditions, but:

• They are often used in conditional or positive–negative selection schemes, and promoter strength is tuned so that selection is effective yet not excessively toxic.​

• There is no universal requirement that every non‑conditional negative marker be under a strong constitutive promoter; weaker or inducible promoters can be used depending on the design.
  Thus D is not generally true.

Why option (1) is correct

• A and D are broadly incorrect.

• B and C are well‑supported by standard transgenic practice and literature.
  Hence, the option that lists all incorrect statements is A and D only (option 1).