I confused on the basic concept of database management system

Ada and Mike share a database file X and execute database queries, T1 and T2, respectively.

Which of the following activities should the database management system NOT do?

(1) When T1 is reading X, T2 is reading X.

(2) When T1 is writing records in X, T2 is writing records in X.

(3) When T1 is deleting records in X, T2 is reading X.

• A. (1) only


• B. (2) only


• C. (1) and (3) only


• D. (2) and (3) only


• E. All activities can be done.

I chose B. Am I correct? Please Explain. Thanks so much.

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An additional question

in situation (1), will T2 be pending when T1 is still reading??
if yes, why situation (2) and (3) are wrong??
or they can be executed at the same time??

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