A). True, arithmetic operators of equal precedence are evaluated from left to right within an expression, according to the standard SQL operator precedence. B. True, multiple parentheses can be used in an expression to change the order of operations and override the default precedence of operators.
C, D, and E are not correct because: C. The + binary operator does not have the highest precedence; multiplication and division have higher precedence in SQL. D. NULLS do not influence the precedence of operators in an expression; they may affect the result of an operation but not the order in which operators are evaluated. E. The concatenation operator (||) has lower precedence than arithmetic operators in SQL expressions.
References:
* Oracle documentation on operator precedence: Oracle Database SQL Language Reference

Explanation/Reference: https://docs.oracle.com/javadb/10.8.3.0/ref/rrefsqlj24513.html

For filtering rows based on the START_DATE within the last 25 months:
* C. WHERE MONTHS_BETWEEN(SYSDATE, start_date)<=25: This WHERE clause correctly uses the MONTHS_BETWEEN function to compute the number of months between the current date (SYSDATE) and the START_DATE column. It checks if the difference is 25 months or fewer, correctly applying the condition.
Incorrect options:
* A: The TO_NUMBER usage is incorrect for date arithmetic in this context.
* B: ADD_MONTHS used in this manner would incorrectly calculate dates in the future rather than comparing past dates.
* D: The MONTHS_BETWEEN function should have SYSDATE as the first argument to calculate past months correctly.