根据句意及首字母提示补全单词。

1. W_____ is your mother's birthday.

2. Christmas(圣诞节) is in D_____.

3. September t_____ is Teachers' Day.

4. My b_____ is October 21st.

5. Dave had a birthday p_____ yesterday.

铜与铜合金焊接时在焊缝及热影响区易产生冷裂纹。