3 . If you think a high-factor sunscreen (防晒霜) keeps you safe from harmful rays, you may be wrong. Research in this week's Nature shows that while factor 50 reduces the number of melanomas(黑瘤) and delays their occurrence, it can't prevent them. Melanomas are the most aggressive skin cancers. You have a higher risk if you have red or blond hair, fair skin, blue or green eyes, or sunburn easily, or if a close relative has had one. Melanomas are more common if you have periodic intense exposure to the sun. Other skin cancers are increasingly likely with long-term exposure.

There is continuing debate as to how effective sunscreen is in reducing melanomas -- the evidence is weaker than it is for preventing other types of skin cancer. A 2011 Australian study of 1,621 people found that people randomly selected to apply sunscreen daily had half the rate of melanomas of people who used cream as needed. A second study, comparing 1,167 people with melanomas to 1,101 who didn't have the cancer, found that using sunscreen routinely, alongside other protection such as hats, long sleeves or staying in the shade, did give some protection. This study said other forms of sun protection -- not sunscreen -- seemed most beneficial. The study relied on people remembering what they had done over each decade of their lives, so it's not entirely reliable. But it seems reasonable to think sunscreen gives people a false sense of security in the sun.

Many people also don't use sunscreen properly -- applying insufficient amounts, failing to reapply after a couple of hours and staying in the sun too long. It is sunburn that is most worrying. A recent research shows five episodes of sunburn in the teenage years increases the risk of all skin cancers.

The good news is that a combination of sunscreen and covering up can reduce melanoma rates, as shown by Australian figures from their slip-slop-slap campaign. So if there is a heat wave this summer, it would be best for us, too, to slip on a shirt, slop on (抹上) sunscreen and slap on a hat.

4 . Last Christmas while staying with my parents, I _______ upon some old love letters that my parents wrote to each other. These letters were all piled up in a basket, dirty and _______. Deciding to read and _______ them, I asked them if I could take the letters back to my Illinois home. They agreed.

As I opened each letter, all of them delicate with _______, I discovered a new page _______ unknown to me in this private _______ of my parents’ lives.

My father used to _______ in the army. So his letters were full of frontline _______ of the things about the war. Each of my mother’s letters was sealed with her 1944 magenta (紫红色的) lipstick kiss. I was _______ to these letters like a magnet (磁铁).

Just six weeks after our Christmas visit, Daddy became very ill and was hospitalized. This time, he was fighting a ________ kind of war. As I sat by his bedside, we discussed the ________. He told me how much receiving those lipstick-kissed letters had ________ to him when he had been so far from home.

It so happened that the next day would be February 14. I chose from the ________ letters the card my father had sent Mother in 1944 and brought it to my father’s bedside.

At his bedside, I joked with him, saying ________, “Today is Valentine’s Day, and I know you have been a little busy lately, but I’ve got you ________.” He became more ________ when I handed him the old ________. He carefully opened the card, and when he recognized it, his eyes filled with tears.

My father, in a voice tight with ________, read the loving ________ he’d sent to my mother fifty-six years earlier. And this time, he could read it to her ________.