3) If she studied more, she ______ (be) a better student.

Привет! Давай разберем эти предложения на условные наклонения (conditionals): 3) If she studied more, she **would be** a better student. (Second Conditional, так как "studied" - Past Simple) 4) They **wouldn't have seen** the Queen if they hadn't visited London on that day. (Third Conditional, так как "hadn't visited" - Past Perfect) 5) If you should win that competition, you **would be** rich. (Future as past/Second Conditional variant, though often considered formal) 6) If I lived in France, I **would speak** French well. (Second Conditional) 7) If they **had locked** the doors, the burglars wouldn't have got in. (Third Conditional) 8) We **will have** a party if Alan passes his driving test. (First Conditional) 9) I **will give** John your message if I should see him today. (First Conditional) 10) They **would not have** any money if their cousin hadn't lent them some. (Second Conditional in the main clause, mixed conditional structure contextually) 11) Those plants **will not grow** if you don't water them. (First Conditional) 12) I would buy that bag if it **were** cheaper. (Second Conditional, глагол "to be" в сослагательном наклонении всегда "were") 13) If she **had opened** the letter, she would have been surprised. (Third Conditional)