Final answer:
The incorrect assumption about DNA prior to the Watson and Crick model is that DNA must be completely resistant to errors or changes. In reality, while DNA replication is typically accurate, the process is not error-free, and mutations can occur, driving genetic diversity.
Step-by-step explanation:
The question focuses on early assumptions about DNA before the double helix model by Watson and Crick was proposed. The one property that was not assumed for DNA prior to their model is option (d): DNA must be completely resistant to errors (change). To function as the genetic material, DNA must satisfy several criteria: it must encode the entirety of an organism's genetic information, including information needed for the assembly of proteins (option b), it must be capable of being replicated so that each new cell receives a precise copy of the genetic material (option a), and it must have the capability for mutation (option c), as genetic variability is a fundamental aspect of evolution and adaptation. Errors are an inherent part of DNA replication; although the process is high-fidelity with repair mechanisms to correct mistakes, it is not completely error-free, which allows for mutations and genetic diversity.