B. had set

Step 1: The table was set before the guests arrived. That is Pattern 1: completed before another action.

Step 2: “Arrived” puts the sentence in the past.

So we need past perfect: had set.

A. opens

Step 1: This is a regular/repeated action, not ongoing and not completed before another action. This is a simple action/habit.

Step 2: “Every spring” shows a general pattern in the present.

So we need simple present: opens.

C. were writing

Step 1: The students were in the middle of writing when the alarm sounded. This is Pattern 2: ongoing action.

Step 2: “Sounded” puts the sentence in the past.

So we need past progressive: were writing.

C. will have completed

Step 1: The report will be completed before a future deadline. This is Pattern 1: completed before another action/time.

Step 2: “By next Friday” puts the sentence in the future.

So we need future perfect: will have completed.

B. recorded

Step 1: This is one single action that happened once. It is not ongoing and not completed before another action.

Step 2: “Yesterday” puts it in the past.

So we need simple past: recorded.

C. are studying

Step 1: The research is happening over time right now. This is Pattern 2: ongoing action.

Step 2: “Currently” puts it in the present.

So we need present progressive: are studying.

B. had written

Step 1: Writing the drafts happened before sending the manuscript. This is Pattern 1: completed before another action.

Step 2: “Sent” puts the sentence in the past.

So we need past perfect: had written.

C. will give

Step 1: This is one single future action. It is not ongoing and not completed before another action.

Step 2: “Tomorrow” puts it in the future.

So we need simple future: will give.

C. will be training

Step 1: The athletes will be in the middle of training at a future time. This is Pattern 2: ongoing action.

Step 2: “This time next week” puts it in the future.

So we need future progressive: will be training.

C. has painted

Step 1: The murals were completed over a period leading up to now. This is Pattern 1: completed before the present.

Step 2: “Over the past decade” connects the past to the present.

So we need present perfect: has painted.

B. were reading

Step 1: The students were already reading when the principal entered. This is Pattern 2: ongoing action.

Step 2: “Entered” puts it in the past.

So we need past progressive: were reading.

C. will have launched

Step 1: The website will be launched before a future point in time. This is Pattern 1: completed before another future time.

Step 2: “Before the end of the year” puts it in the future.

So we need future perfect: will have launched.